I think Grigg is right on with the axle swap advice. I have a 1937 1.5 ton and I put a 1 ton (Corp 14 full floater)in the rear. Was the easiest swap ever - the leaf springs centering pins dropped right into the 1985 chevy 1 ton axle. The dimensions never changed in 70 years. If your running a stock drive train you will have a drive shaft issue. I have a small block and turbo 400 trans in mine.

Hope this helps.
Jeff

1937 Chevy (converted to 4x4)
1942 Chevy G506 1.5 ton 4x4
1958 Mack B model (on Chevy 1 ton 4x4 frame)
1969 Dodge Charger
1987 K30 Crewcab