The standard-equipped factory tranny in the '60-'66 Chevy 4x4 trucks is the SM420, granny-low 4-speed. The transfer case is the divorced style and is a T221. I am not able to speak to the fit of a Blue Oval powerplant in a Chevy truck, however, with a divorced transfer case, the connecting link is the front driveshaft, so there are no bolt patterns to match.
FYI, with low production numbers and survivors becoming more difficult to find, the '60-'66 Chevy 4x4 trucks with factory running gear are getting more difficult to find. From an economics standpoint, the truck is an appreciating-asset, if left unmolested, with original running gear.
