The 617a is the turbo version. There is an extra sprocket on the crank that drives a chain driven oil pump, that is why the crank is longer. There is a 1" spacer plate on the front of the block and the oil pan has a 1" extra lip on the front edge. By stripped block I mean I don't have any ancillary parts. So I am trying to utilize all the parts from the 617 na motor. It all should work except I need to figure out a different harmonic balancer/crank pulley set up to make it all work. Hoping another G owner who has done the swap can post a picture of theirs.