Best fit, 3-53 or even 2-53
Best bang for the buck, 3-53T.
Transmission, probably overdrive unless you choose a rear axle with some very fast ratios available.
A 6 speed would be nice for the closer spaced ratios.
Easier fit is special two piece flywheel housing and flywheel Detroit offered for conversion in trucks years ago, two sizes of GM housings. The small one fits angled rear engine mounts in 1954 and later small trucks, standard transmission pattern same as SM420.
Larger GM housing fits angled rear mounts in larger size trucks same time period, same transmissions fit and also Spicer 3000 series (has dual pattern).
No input on 4x4, probably more trouble than it’s worth.
Grigg
