geterdun
+1y
you can put in a GM 4.3 Vortec, built to feed your power choice....... and it fits like it was made for it, no modifications. Use Mazda radiator, if it is all metal, loss it if plastic. Even use original mounting engine mount locations, make "U" bracket to cradle '77 GM mounts, started having broke motor mount "kickup" stopper when you nail it. Make the "U" brackets, bolt to engine mounts bolted to engine, lower motor on them, chalk through the frame holes, pull 'em, drill 'em with holes to move them (slotted side-wise if capable, frame is vertically, I think.), bolt the engine in. Later, if engine is where you want it, weld them.
Transmission and transfer case, no idea, not a four wheeler, just a few extended cabs.