i dont know if the 6 cylinder trucks are the same, or 60s trucks for that matter... but with chevy generally everything fits everything else lol
i run an 87 chevy 1500, i took out my old blown up 350 and dropped in a 427 big block tall deck out of a dump truck, thats how interchangable everything is. lol
have you checked to see if its a bolt in or not?
is the bellhousing the same? most generally is with chevy.
if it doesnt fit, bolt your motormount to the side of the block fully assembled, drop the engine in , bolt it to the tranny , get everything lined up and weld the mounts to the frame. can be done in a couple hours, piece of cake.