motor swap

I have a 1986 2500 350/350 gmc truck with a rod knock.OK I have an offer to buy a really tight 350/700r4 combo out of a 1996 chevy blazer ----now for the question will they swap right out? or will the drive line have to shortened or lengthend?will the tranny mount work?and if not will the 350 from the '96 bolt to the tranny from the '86?Any and all replies would be appreciated.Thanks everyone

I know this is an old post, but just in case you're still looking for an answer, I'll try my best. The '96 350 will bolt up to the '86 trans. The '96 trans will fit the '86 with mods to the mount position and a shorter driveshaft. Your biggest problem involves electronics. The '96 engine has EFI and the transmission is computerized. The intake and carb from the '86 won't bolt onto the '96 engine's Vortec heads either. You will have to swap cylinder heads from the '86 or transfer all the electronics from the donor vehicle.

what type of motor and does it have an engine number