What 5 spd for AMX

3.73 should be good with an OD five speed. Most use rear axles in the 3.55-3.73 range, a few as high as 3.23 -- depends on the OD ratio, trans first gear, and tire size.

I have 3:73 gears. The first is just way too tall. If I went any lower on the rear I’d be running 3500 rpm at 55mph...

Simple -- lower the REAR AXLE GEAR and use a GV unit. Most OD cars use a lower rear axle gear than non-OD cars for this reason. You have to be turning 1800-2000 rpm (depending on cam/tune) to cruise, so the rear axle is geared for whatever your typical cruise speed is around 2000 rpm. This gives you a lower first gear by way of a lower geared rear axle. A torque cammed motor may pull well below 2000 rpm, some as low as 1500-1600, but the engine has to be built to pull that low. Ideally you want to be 200-300 rpm into the torque band where it's making good pulling power. To close to the low end and you limit how much you can slow below desired cruising speed without loading up the engine. Case in point -- I ran 3.08 gears with an AW4 and 4.6L stroker. It would happily pull down to 1500 rpm without lugging or complaint, but it was obviously working harder running 60-65 in OD rather than 70-75. I swapped to 3.55 gears (wstock for a Cherokee w/4.0L and AW4) and average gas mileage went UP by 2 mpg. 3.31 gears would be better on the highway, as it turns a bit more than I'd like at 75 (over 2400 rpm... the Renix EFI starts to enrichen the mixture at 2400-2500 rpm). I usually cruise at 65-70 though it will happily cruise at 75-80 all day... jut drink gas doing it between enriching the mixture and aerodynamic drag... about the same as an XJ Cherokee.

Only problem with a GV unit is the cost -- it's just about as much as swapping in a five speed.