I run an 89 Cougar in the 24 hours of lemons with a 5.0 out of an explorer and an M5R2 trans. We typically run 3.27s with the M5R2, which would be comparable to 3.73s with a 4R70 or T45. I highly reccomend converting to a T45 and getting a chip for the ECM to get rid of the speed limiter and deal with any issues with the trans swap. With the ECM mounted, and some duct tape over the chip, we have never once had an issue with the BS judges noticing it or taking issue with it. As far as a trak-lok goes, our trak-lok unit has held up just fine, and in fact it was still holding fairly well when we boiled the gear oil out of the rear diff. We rebuilt the diff and set up a cooler for it to stop that from happening again, and we used 3.08s this time just because we had them laying around, but we really lost speed from it, so we'll be going back to 3.27s for the next race, which is the Capitol Offense in June.
I would like to know what brakes you are running, since with my diff sorted out, that is now my major issue. We initially were wiping out front pads, so I put on some Hawk racing blues, and they almost made it the whole day, but were metal to metal by the end of the day on Sunday, and we also went through 3 sets of rear pads over the course of the weekend. We are also running 13" Cobra front brakes and 11" rear cobra rotors with stock 94+ tbird rear calipers relocated out to clear the rotors. Like you, we have no problem outbraking most cars on the track (though the little 190 benz's still outbrake the hell out of us), and with the 5.0 and 5-speed, we can out-run everyone on the straights no problem, and now that I finally put sticky tires on the car, we can out-corner most of them too, so at this point our only obstacle is keeping the car on the track instead of in the pits or penalty box.
-91 Cougar LS, coming soon, complete overhaul
with a 427" Windsor.
-90 XR7 5-speed black on black w/sunroof, MP2, coated rotors, double intercooler, 15%OD, ported heads, comp stage 1 cam, 85mm TB, 90MM LMAF, 80# injectors, and ported big valve heads
-98 Mark VIII LSC, Procharger P600b, TR3650 swap and 3.73s.
-90 SC Automatic rustbucket winter beater
-97 Tbird Sport 4.6 Nice weather daily driver
-"Your buddy Mike is INSANE!" -ClintD's dad