Re: 2.87 diff. for the crossfire
A 2.87 would be close though a 2.73 would be better, without a body mod can only increase the rear tire diameter about an inch.
The problem is that this is not a real 6 speed (5th is 1:1) but a five speed with a granny low. The jump from fist to second is almost 2:1 and while flywheel inertia limits the speed the engine can accellerate, it works against you on a hard 1-2 shift (back in the day we used to lighten flywheels A Lot to compensate).
On the other end, while a 7.6 cDA isn't bad (not great, my Fieros were 6.75) but OK, the 3.2 has plenty of torque for a 1900 rpm/70 mph cruise. Engine would be more efficient there anyway.
Keep in mind that the purpose of an OD is not top end but a relaxed cruise and for our engine geometry (3.3" stroke is near ideal for gasoline) a sub-2000 rpm cruise at 70 mph would work very well.
Math isn't simple, tied up the GMI computers for quite a while in the early '70s calculating ideal engines/trans for different conditions. Since was going to school in Michigan and home was in Florida, many hours at cruise was important to me. Had a 67 Camaro 327 with a late Rochester FI, four speed, & free flowing exhaust that turned in some amazing numbers but had real Sunoco 260 then.
ps I also use OBD-II for RPM and GPS for speed. Is close enough for government work.