[chevyrestoguy]

I'm running a small block with a 700r4 in my '64 LWB, and I found a combination of factory shafts that worked perfectly. No cutting or mods.

Front shaft: 1973-1987 1/2 ton Suburban (or maybe C-10 LWB?)
Rear Shaft: 1960-1966 C20
Carrier bearing: Heavy duty 1960-1966 "C20 style" (shaped like a bell).

You will need to run a "combo" u-joint (1310/1350) at both ends of the rear shaft if you are using a stock truck 12-bolt. At the slip joint, use the yoke from the '73-'87 rear shaft.