I am doing pretty much the same thing to my '37 Special. For a rear axle I chose a GM 10 bolt w/4:11 gears. These are cheap, reliable, and easy to find in many gear ratios. You will need to add ladder bars to locate the rear end since that is the function of the torque arm that you are removing.
You didn't specify manual or automatic, but I chose a T-5 manual from a V-8 powered Camaro
. These can be had for under 400 bucks and will handle the torque. I would not suggest using the V-6 or 4 cylinder T-5 because it will not handle the torque. With the Camaro tranny you will need to replace the tail housing with one from a truck (S-10 or S-15) to move the shifter forward.
To mate the tranny to my '37, I had to bore out the bell housing, weld up and redrill the lower 2 transmission bolt holes, remachine the stock flywheel to mate up with the Camaro clutch disk and pressure plate, and make an extended pilot bushing due to a slight difference in main shaft length. I am also using a hydraulic throw out bearing for ease of use and assembly.
This is not a cheap modification. I am doing most of the work myself but still have about $2000 in parts and machine work involved, but I rebuilt the axle and tranny adding about $800 to my costs.
