for tranny it would be the SM420 your right about the engine choices as for the rear end i think chevy quit using the eaton rear end in like 63 but i took a tranny out of a 67 3/4ton chevy and it had the bolt out 3rd member but if its your average old 1 ton farm truck my money goes with it has the 292
Nate


Link to my photobucket for pics of my vehicles
http://s238.photobucket.com/albums/ff17/OldIronChevy/