i have an 86 and an 81 sierra. 86 has good body but blown v6 motor. 81 has rough body and good straight 6 motor. my question is what would be easier... swap the truck bodies or swap the engines and trannies etc.?

Well swapping the engines and trannies would be easier and less involved in my opinion. But honestly, sell them both and buy an 80' somethin with a 350 in it.

Should be able to just do the motor swap the tranny's should bolt up.