Thomas,
Any '48 to '54 1/2-ton 4-speed should be a direct bolt-in.
The '48-'53 3/4-ton 4-speed also had the enclosed u-joint, and should work;
The 4-speed from the larger trucks had open driveshafts, and aside from that, are the same tranny.
Your limiting factor here is finding something that will adapt to your existing tourqe tube rear.
Is your 3-speed beyond re-build?
