Bubba had a fairly successful autocrossing debut. A lot of that was due to the talent of the various drivers, but the car and preparations had a hand as well. Since lots of people call or mail to ask about the work I've done on Bubba, I thought I'd write up a quick summary of the changes we've made. Parts were obtained from many sources, mentioned in the text; you can find contact information for them in the Monster List of Vendors. Some parts were custom made by or imported through Team Fat.
Autocrossing is not road racing. While some factors are similar, the demands on the car are different. In road racing, there is usually time between turns to get the car out of one turn, then positioned for another. The motors are tuned to rev high, and produce power at the upper end of the rev range. In an autocross, there is little time between turns for the car to settle down, quick transient response is crucial. And with a dearth of long straights where the car can make use of all the revs available, one needs to have as much low and mid-range grunt coming out of the turns as possible.
Bubba is build to SCCA C Street Prepared (CSP) rules. A car for this class is capable of being street legal, with full interior, lights, wipers and such. The engine internals must be stock, but intake and exhaust systems, with the exception of forced induction, are pretty open. Suspension is quite free also, in terms of bushings, springs and shocks. Wheels are unrestricted, but tires used must be DOT rated. Several manufactures do make DOT tires for racing, such as the Yokohama 008R, the BF Goodrich Comp T/A R1, and the Hoosier Autocrosser. Not too good on treadwear, but do they stick!
I'm going to go through this in the approximate order I did the work, and in the approximate order of importance. The best thing you can do for your car's autox performance is upgrade the rubber and the shocks. The best thing you can do to improve power is the make the exhaust system more efficient. Those are the two things that give you the biggest bang for the buck; everything else is good, but the law of diminishing returns applies.
The tires on the car are Hoosier Autocrossers, in 185/60-13 size. 185/60-13 are a little narrow by CSP standards, but I chose them because they will fit under the stock wheel wells with no external changes. The inside lip of the fender opening has to be rolled up (use a baseball bat and patience). They are mounted on lightweight aluminum three piece wheels made by Kaizer; 13x6 with a four inch backspace. These dimensions were chosen to support the 185 tires and fit under the wheelwell; the four inch backspace is the maximum that will clear the rear shock absorbers.
All the shocks are SPAX adjustable units. The fronts have adjustable spring perches (for setting ride height) and are available from several sources; I got them from TRF. The rears are a special kit from TriumphTune - instead of the stock top mounting location which welded to the wheel well, these are shorter and connect to a bracket that is bolted to the frame. When installing the shocks, make sure that the adjusters can be reached easily afterwards! When autocrossing, the front shocks are all the way up, and the rears full soft. For driving on the street, I usually set the fronts at about 5 clicks.
Suspension bushings in the front have all been replaced with custom items made of black delrin. Similar bushings in urethane are available from Chris Witor. The rear bushings are uprated rubber (from TriumphTune), because they must all allow axial movement (when the radius arms are adjusted) as well as radial. Front sway bar bushings are in urethane, from British Parts NW. When installing the urethane/delrin bushings, lubricate the interface between the steel sleeve and the bushing with some sort of synthetic grease, or they'll squeak horribly after a few hundred miles.
Front springs are the 330 pound TriumphTune units with a 7.5" fitted length. They could be stiffer and shorter, but I like to drive on the street. Sway bar is 7/8". There's no rear bar at the moment, though I'm thinking about it. The rear spring is reconditioned stock rear spring. It's a little weak; the reason the rear shocks get set full soft is that there's too much rear roll and the inside wheel picks up. Setting the shock soft is an attempt to keep the wheel down as long as possible. A rear bar or a stiffer rear spring may help.
A nice touch in the preparation of the front spindles is deleting the OEM inner wheel bearing seal - the felt and steel parts always separate, the felt crushes down and stops sealing. There's an industrial kind of seal, called a "Nylos" seal, which is two pieces of stamped sheet metal. These seal very well, don't deform after time, and allow the bearing free play to be set repeatably. Dave Bean Engineering has the right sizes for Spitfire and GT6 hubs in stock, since the parts are shared with the Elan and Seven. I use RedLine synthetic CV joint grease here.
Triumph went to a different spring on later GT6s for this reason - a "swing spring". It is possible to update the Rotoflex rear suspension with a swing spring, but you must find the correct one: I was not aware of the fact that there are several, bought the wrong one, cleaned and painted it, and only discovered at the last moment that it fouled the rotoflex couplings!
Front camber is about -0.5 degree, with some toe out. This is another reason to choose the Hoosiers - they're bias ply and don't need a lot of camber, which is good since the Triumph suspension can't provide much. (For example, Yoko A008s like about 3 degrees of static negative camber - you can't put in that many shims!). I run with a touch of toe out at the front and zero toe at the rear.
For a long time, I ran brakes stock, with two changes: all the flexible lines have been changed to stainless steel/teflon (I made my own, but TRF will sell you a complete kit), and the front pads are Carbon Kevlar. I started with the softest ("orange", I think) compound from Cool Carbon; I'm sure other people are selling the same compound as well. This is the one that is advertised as for racing purposes only for light Formula cars. It's perfect for autocrossing and the street, though there is a fair bit of squeal and LOTS of dust. No one sells pads for Triumphs, but the 240Z pad is an exact fit.
The Cool Carbon pads performed very well, but I got tired of the dust. I've switched to Porterfield R4S pads this time - I've had very good luck with them, and they are the lowest dust and most rotor-friendly pads I've used.
I finally managed to upgrade to Toyota four-pot calipers, as described here. The kids at the parts counter will want a specific application, so I told them "1981 Toyota Hilux 4WD non-diesel". I think there was an engine choice, but it doesn't matter :-). The Porterfield part is AP137.
The calipers mount up fine, clearing the dust shield without trimming. They clear the wheels no problem - even the stock wheels. Unfortunately, the brake pipe fitting intrudes into the springs at fully lock - the pipes leave the caliper at a 90 degree angle to the body, straight out.
I then tried a banjo fitting, since they don't extend out of the caliper as much. That requires shortening a standard banjo bolt, so it doesn't bottom at the inverted flare fitting. Oh, and machining a flat on the caliper so the crush washers will seal. And the head of the banjo bolt will still interfere with the spring at full droop combined with full lock. Oh well. It's possible that one could take more out of the caliper mounting boss, and thin the head of the banjo bolt, but now you're changing a bunch of engineering parameters associated with the braking system... not for the faint of heart.
That led to try to find some way to adjust the end of the steering range. The rack is round, 13/16" diameter. The passenger side needs about 1/2" less travel; on the driver's side, it's more like 7/8" because of the way the rack end is belled there. I ordered some two-part shaft collars, but they have two problems: they only come 1/2" wide, and the OD is 1-5/8". That's really big to get the dust boot over on the passenger side, and doesn't really fit in the bell of the driver's side very well. And I wasn't particularly happy about not having a positive stop against the inner ball joint, just in case something slipped.
While staring at this, I realized that I have a drawer full of hose clamps that are roughly 1/2" wide! In fact, there are two designs - one where the band narrows under the bolt machanism, and one where the housing extends beyond the band. So one is about 1/2" wide at its widest, and the other is about 7/8"! This worked perfectly. The parts are small enough that they can be slipped under the dust boot easily. Now I have no potential interference issues with the brake lines!
The rear brakes are stock, adjusted every event.
To combat the wheelspin caused by lifting the inside rear while cornering, I have installed a Quaife limited slip center section in the 3.89 differential. This solves the wheelspin problem quite nicely, and also does away with the weak spider gears that are a traditional problem in the GT6 driveline. (The Quaife won't fit the 3.27 diff, if that's what you're running.) The Quaife is a big ticket item, at least $700, but makes a huge difference in getting the power down at corner exit. (I used to sell these through the Dimebank Garage, but demand was too low for me to keep them in stock. The best source at the moment is JAE, who will import one for you. Don't pay the price that Moss asks!)
While I was at it, I replaced the intermediate drive shaft flange bolts (Triumph p/n 132023) and the propshaft flange bolts (p/n 144961) with with aircraft bolts and higher-temp nyloc nuts. There is no dimensional difference between these two bolts; both are dead ringers for an AN6-7A bolt, 3/8-24 thread, 5/16 grip, 61/64 length under the head. The only visible difference is the marking on the head; the 132023 has none, just a large circular depression, while the 144961 is marked "ARB S". Perhaps someone in the UK is familiar with that marking, but I can't find it listed anywhere.
I was never completely comfortable with the stock bolts - even though they are a "special part number", they appear to be grade 5 and have a threaded portion bearing on the flange. In addition, the standard nyloc nuts tend to come loose with time, something I attribute to the relatively high heat in this area from the exhaust system. The 5/16 grip of the stock bolt leaves one or two threads inside the flanges - this is probably the highest stress area on the bolt, and seemed like a bad idea. I replaced them with the next size up, AN6-10A, which has a 7/16" grip. Running clearance is fine, though installation is a bit fiddly. This leaves a small amount of unthreaded shank showing, so it takes a single AN960-616 washer under the AN365-624A nyloc nut. I considered using the thin AN960-616L washer and the half-height AN364-624A nut, but the nut is rated for shear loads only. Even though the torque is transmitted in shear, there's a fair bit of clamping going on as well.
The other weak spot in the drive line is the transmission. There's only so much you can do - we haven't yet found a Japanese five speed that will fit in the place of the original tranny, but we're looking. (But see below!) For the time being, the best bet is to build an uprated box from the best pieces available. This means a the input and layshaft from a GT6 Mk.3 gearbox, Spitfire 1500 mainshaft, a few pieces from the TR7 four-speed, and the original close ratio gears and case. I used to assemble these for other people, but there hasn't been much demand and my parts stocks have dwindled. John Kipping in the UK will sell you one for a good price, along with an uprated overdrive if you want/need it (I don't recommend using a D-type to race).
Any flywheel is allowed, and I have gone with a lightened stock unit, since I like to drive the car on the street. A dedicated autocross car would probably go to an all aluminum one. The stock clutch is controlled with stock hydraulics cylinders, but I fitted an adjustable pushrod and a remote bleeder.
As stated earlier, the car is built to SCCA Solo II rules for the Street Prepared class. The VTR Modified class corresponds fairly close to this, with more liberties available to the VTR competitor. Since Bubba is built for SCCA racing, the stricter rules apply. First off, no internal engine modifications are allowed, other than a slight overbore of the cylinders, and a maximum of 0.010" removed from the cylinder head. The valvetrain, camshaft, pushrods, rockers, and springs must all be stock, no fancy race cams allowed.
That said, the head has been port matched (within the 1" rule) and shaved. The rockers were rebuilt by Rocker Arm Specialists, who do a lovely job, including moly coating the components to help reduce friction and increase life. There's also an external oiler kit from TriumphTune to try to keep the rockers alive.
The engine internals have been prepared to the limit of the rules - that is, they've been balanced. I had the second rings converted to "gapless" by Total Seal; this keeps the leakdown to less than 3% and gets more of the energy into the driveline instead of past the rings. I removed the stock fan and fitted an electric fan with thermostat - the stock fan was eating about 7 bhp and noticably slowed down the rate at which the engine could rev! I haven't gone to the effort of opening the bores out the the .040" over that's allowed. I have gone to the double row timing chain setup from a TR6, which is not completely legal but gives me peace of mind. It's also a good idea to bore the block for Spitfire camshaft bearings and to pin the crank thrust washer.
The focus must be on breathing, which makes quite a difference in overall power and throttle response. The first change to make is in the exhaust. The stock exhaust manifold is a joke, and the exhaust piping is worse: for starters, the down pipe takes a luxurious bend under the gearbox, which just makes the problem of hot gearbox oil and slipping overdrive worse.
I fitted the TriumphTune "Extractor" manifold, which is designed for improved midrange to top-end power, as opposed to their "Sprint" manifold, which is designed for ultimate top-end. This fits very well, but it's tight. I finally ended up grinding away a little of the frame where the headers pass it, since there would occasionally be clanking while starting. I had the headers Jet-Hot coated, to improve their life and to reduce the underbonnet heat as much as possible. The rear of the header collector ends at approximately the rear of the gearbox.
This is connected to a custom exhaust. The piping is 2" aluminized steel, which is run down the passenger side of the frame, under the halfshaft, and bends towards the right rear corner of the car. This exits through a SuperTrapp muffler (4" diffuser disks, I run somewhere between 7 and 10), mounted with the ST hanger off a small bracket that's attached to the stock muffler mount. The exit of the muffler is just past the body at the back corner. This configuration was chosen to avoid all the grinding and scraping I got when I would go over curbs with the ANSA system. It's all held together with stainless steel hardware and SS band clamps available from Dave Bean. The ST sounds great, very distinctive, but not very buzzy or intrusive while in the car. (Get on the throttle, though, and it will set off car alarms!)
I ran the car with the stock 1.5" Strombergs for a long time, but they really aren't good enough. If you are running the Strombergs, you can help yourself quite a bit by cobbling up a cold air intake - get two pieces of Aeroduct (or the cheap J.C. Whitney substitute) and some hose clamps, and make two snorkels from the forward intakes on the filter box. Use Adel clamps to fasten these down somewhere in front of the radiator. This will provide a good supply of cold air to the carbs and reduce the engine's tendency to ping under load (especially when hot).
Right now I have the triple Weber setup - three 40 DCOEs mounted on the TriumphTune stepped manifold (it's stepped to clear the bonnet - the TR6 manifold won't fit). This took quite a bit of work to make fit properly; the air cleaner is a custom assembly with an airbox over the carb throats and a remote ITG filter that draws air from in front of the radiator shrouding. I fiddled with this off and on for a year before I was completely happy with the operation. It is not the setup for the budget-minded or impatient. However, it is a HUGE improvement over the stock carbs.
The triple Webers currently have the following:
|Main fuel jets||110|
|Air correction jets||160|
If you're looking for middle ground, I have heard good things about taking SU HS6 carbs and mounting them (with adapter plates) on a slightly modified stock manifold. The fit is quite tight, but you get a great improvement in breathing. TriumphTune has the adapters (and the carbs, if you want to buy new). I would recommend putting K&N stub stacks on the carbs, but I wouldn't recommend using the K&N filters (I have heard too many reports that they flow well but filter poorly). I'm very very happy with the reusable foam filters from ITG.
The ignition system is a rebuilt stock Delco distributor, with vacuum advance hooked up but retard disconnected, and a Crane HI-6 spark box. The Crane is a good solid unit, offering the advantages of a multi-spark capacitive discharge system, as well as a built in, easily adjustable rev limiter. I mounted it on the vertical panel next to the driver's left leg; getting at the rev limiter adjustment is not easy, but it's doable. At the moment, I'm triggering with the stock points; they're don't bounce until around 7000 rpm, and the HI-6 puts very little load through them so they don't need to be adjusted often. The HI-6 also determines the dwell, so a little wear in the distributor bushing doesn't matter. I still want to try a Pertronix ignitor, though.
Cooling the engine is critical - the GT6 has never been known for its oversized cooling system, and getting more power out of it just makes the problem worse. The new fan is a 10" unit from Racer Wholesale, mounted behind the radiator. It just fits in front of the pulley, on custom brackets that have been silver soldered to the radiator frame. It is controlled with one of the RW thermostatic switch units, as well as a dash switch for override. I started with a 12" fan mounted in front, but that blocked the radiator airflow sufficiently that the fan would come on while cruising at 60 mph on a cool day. With the 10" fan behind, this doesn't happen, though the fan runs a lot in traffic. The radiator just isn't big enough, but CSP rules say I can't change it. I may have to revisit the shrouding I have - make sure yours is intact! (If I had it to do over, I'd get the high efficiency bladed 10" fan from Scotts Manufacturing, which will move more air than the SPAL unit from Racer Wholesale. Or go back to the 12" in front and live with the fact that the fan cycles from time to time; it's a worthwhile tradeoff for keeping the engine cool in traffic on a hot day, and a much less fiddly installation.) The temp gauge tends to sit at the 2/3 mark, creeping up to and past the 3/4 mark on hot days.
I also added an oil cooler in a custom frame, designed to just nestle into the radiator support bracket. The cooler sits vertically on the driver's side of the radiator. The inlet is at the bottom, with a check valve to prevent the cooler from draining while the engine is off. There's a Mocal cooler thermostat, a temperature sender, and the TRF oil cooler and spin-on filter adapter kit, along with plumbing made of Earl's super stock hose and -10 fittings. A FRAM PH3614 filter just barely fits. Despite an anti-drainback valve, there's still a little bearing knock at cold startup, but it's much improved over the stock setup and the oil pressure stays at 60 psi hot with Mobil 1 20W-50, though it drops below 30psi at idle hot. I have a slightly modified Smiths "safety" dual gauge in the dash that shows oil pressure and temperature. In addition, I have changed the oil pressure "idiot light" switch to one that comes on at 30psi instead of the stock 7psi, and added a line to feed extra oil to the rocker gear.
I run Mobil 1 oil, which may actually be reducing the amount of heat that is removed from the engine via the oil cooler; it is known for heat rejection. But it is also known for protecting the engine.
I ditched the stock fuel pump and went to a Facet solid state pump. This is mounted inside the frame rail near the left rear wheel, with the Facet in-line fuel filter. There's an aluminum rock shield around it. There's a small inline filter in the engine compartment, just upstream of a Holley fuel pressure regulator. This has an integral pressure gauge and is set to 3psi. The fuel line runs across the bulkhead shelf to the carbs, so it's kept much cooler than the old routing which went around the front where the hot air from the radiator blows over it. Power for the pump is taken from a "green" circuit, and runs through one of the inertial cutoff switches from Moss. I had to modify the switch to have heftier wires, since it came with 20 gauge leads; wire this circuit with 16 gauge. The cutoff switch is mounted next to the fuse box.
I've upgraded the headlamps with a relay on the high beam circuit (you can see it just left of the brake master cylinder), Cibie Z-beam lamps and 100/55 bulbs. I also added some small projector fog lamps under the bumper, just inside the overriders; these are wired with a lighted switch in the dash, powered from the parking lamp circuit.
I've made a number of modifications to the interior - mostly small, but significant. I'm using a 11" semi-dished leather-covered steering wheel made by Mountney, purchased from Demon Tweeks. This is a recent change; before I was using a similar Mountney 13" wheel, purchased through the Triumph Sports Six Club, because it's the only way my knees clear comfortably - it also makes it possible to heel'n'toe for downshifting. The extra inch makes a big difference - with 13" I was fairly comfortable, but the 11" wheel lets my hand clear my thigh and makes it easier to fully apply the brakes. You can see the square illuminated fog lamp switch above the wiper switch, and the illuminated fan switch at the left edge of the dash; it is just barely visible when seated.
I added an extension to the accelerator pedal, making it about twice as wide. This makes "heel and toe" downshifts much much easier. I also added a dead pedal next to the clutch, using the dipswitch pedestal from a TR4A. The whole pedal arrangement was narrow to begin with, and this doesn't help - wear skinny shoes!
I also added an adjustable pushrod and matching clevis to the brake master cylinder. This allows me to get the pedal heights just so. It's quite difficult, actually, to get the throttle pedal height such that you can get full throttle (there's lots of flex in all the linkage) and also position the brake pedal such that you can do proper heel-toe. The brake pedal ends up being quite high relative to the clutch pedal.
It's important to adjust the throttle linkage carefully. The stock linkage has some play designed in at idle; make sure it's there, and make sure that the off-idle actuation is even. The ball end at the end of the long horizontal link is subjected to high temperatures from the header, and wears a flat spot. I replaced this with a small spherical rod end (from Small Parts). You don't want to use Teflon here; it doesn't like more than 400 degF or so, and it's really close to the header!
The carpet underlayment has been replaced with Reflectix, bubble wrap that is coated on both sides with aluminized Mylar. This makes the cabin not just tolerable, but pleasant! We've driven the car in 100 degree weather without adverse effects; before this change, we wouldn't have considered doing so. Covering the gearbox cover in this (and making sure it is well sealed to the car) made an enormous difference in cabin temperature.
The gauges have been supplemented with oil pressure and temperature (via a Smith's "safety gauge", modified to have the proper color scheme), Lucas ammeter, and a VDO quartz clock. In addition, I reversed the fuel and temperature gauges - this way, the more important temp gauge is always visible, no matter where my hands are on the steering wheel.
There's a fire extinguisher mounted under the passenger's knees; it's close enough that the driver can reach it while belted in.
Dave Bean Engineering have a Metalastik coupling for some Formula Ford applications that will also fit the GT6; it's supposed to be considerably stronger than the stock party. DBE's part number is 035D0035 and they are $79.90 each (in April 1999). I haven't tried these, because I'm afraid that I won't be able to deflect it enough to get the spring and vertical link reattached (always a problem on my car).
Grassroots Motorsports did a series on putting a rotary engine into a Spitfire, including a very tidy conversion of an RX-7 differential to fit the Spitfire rear end.
Apparently folks Down Under make a habit of installing the Datsun 510 rear end (or its descendant from a Subaru, which is used in the rear of current 4wd products and is reputed to have better oil seals). The diff is supposedly an easily adapted bolt-in, with good parts and LSD availability. The diff is asymmetric, so the half shafts must be different lengths; you will need an adapter to replace the Rotoflex couplings. One trick way to do this is with th CV joints from a Supra, which bolt up to a plate rather than going onto a splined shaft... or take a look at this very sweet installation complete with custom casting to center the diff and mount it up cleanly (yes, I've been told they're for sale).
Barry Schwartz has built a lovely Spitfire with a V6. Of particular interest is his rear end choice - a GT6 diff with TR6 halfshafts. Photos and discussion can be seen here.
Many years ago, Group 44's SCCA championship-winning car adapted a 240Z rear end to increase reliability. I've corresponded with the owner of a GT6+ raced in that era, and he reports a similar conversion, with "quite a bit of fancy welding". Ted Schumacher indicates that the stub axle can be machined to take a TR4 pinion flange, which will bolt right up to a Datsun 510/early 240Z halfshaft (which will bolt right up to the stock diff output flange). Then all that's left to do is get the halfshafts shortened the appropriate amount to fit. Corvair stub axles are an alternate starting point for building an appropriate stub axle.
Clive Averill ((303) 420-3062) sells a CV joint conversion that replaces the rotoflex joints; it's reported to be a very tidy job that works well. You can see some photos of it here. Not cheap, but racing never is. This can include adjustable aluminum lower control arm and radius arms. Joe Curry reports that fitting uprated axles from Moser Engineering is a nice finishing touch for this conversion; see pictures pictures pictures here. Joe also sells an improved shock mount for rotoflex cars.
There's lots of lightening that could be done. The battery could be relocated to the spare wheel well. There are more robust transmissions that fit with work - I know that the TR4/6 non-OD tranny will (the factory raced Spitfires at LeMans with a TR4 tranny) but I'd really like an overdrive to go with the 3.89 rear axle ratio. There's a fellow in New Zealand that operates a company called Conversion Components that has engineered a lovely looking swap with a 5-speed Toyota 2T 'box, but I'm too far away to do the remote development (and he wants $800 for a kit, plus the tranny!). I've heard stories about fitting a Rover 5-speed unit (some firewall surgery required), one of the Toyota boxes with integral bell housing, and even adapting a T-5 ... and after years of hearing stories, here's someone who's done it with a T-50 and documented it! John Pritchard - The Sports Car Factory, Hallville, Ontario - has been reported to stuff BMW 5 series 5-speeds in ("they're cheap, compact and robust"), as well as Volvo four speeds with overdrive in fourth, though I've never managed to connect with the guy to confirm this or find out details. In the UK, Frontline Spridget sell a conversion kit for a Sierra 5-speed to a Triumph/Spridget 1500 engine, and might be convinced to do the same for a GT6. John Esposito of Quantum Mechanics Connecticut is reported to have a 5-speed conversion based on the T10 transmission for Spitfire/GT6.
Ted Schumacher tells of running the ex-Group 44 GT6 at Sebring in 1978: "We were running the ex_Group 44 GT6 as an IMSA GTU car. We had a Muncie M21 c/r 4 speed with Hurst shifter. Merely a matter of an adapter plate between the GT6 bellhousing and the gearbox and a correct spline size in the clutch disc. Even used the GT6 clutch hydraulics. Great gearbox. We lost the rear disc brakes at Road Atlanta and drove the reast of the race with the gearbox as brakes. Very interesting on that course. Found out we were a whole lot faster than Paul Newman (Bob Sharp GTU entry) through turn 5. He had brakes and could slow down much better than I could. The car had a 2.5 engine, 4 wheel disc brakes, 10" wide rims, diff cooler, etc. Fun ride and a real rocket ship. " So it's not hard to put in a Muncie if you're worried about reliability, but he'd start with a Toyota truck 5-speed if you really want overdrive. Herman van den Akker has a complete kit to achieve that, with new ratios available over the counter from Nissan dealers.
Recently, Quaife have started to advertise their gearboxes more heavily in the US. There's a photo at Taylor Racing of a Quaife tranny bolted to a GT6 bellhousing! This is probably a good solution for an autox or road race car which does standing starts; the ratios may not be so useful for rolling starts. An acquaintance who races a GT6 in GT3 likes the Saenz gearbox, but it's a straight-cut dog engagement box that is certainly not suitable for the street.
While it is true that autocrossing is one of the least expensive forms of motorsports, it is still easy to spend as much money as you'd like on car preparation. I like to tinker, and I've made the mods over a period of many years. Some of the things I've done have been quite expensive in parts (the Quaife leaps to mind), and I've put hundreds of hours of labor into the car, and probably thousands of dollars into machine work for the engine and other parts. If you were to ask the Dimebank Garage to build you a duplicate, it could easily end up costing $8000 or more. I could be persuaded to sell Bubba for less than that, since I'm looking to move on to other forms of racing. If the price seems too high, compare it to the cost of buying a good donor GT6+ and buying the parts (and building an engine). Or ... compare it to the cost of a new Miata or Neon ACR, cars that Bubba can outperform.