4 Speed Conversion

I believe all the 340 cranks up to 1972 were forged cranks and were drilled. What I don't know is if they were all finish drilled to accept a pilot bushing, or if they were just "Pre-drilled" with a smaller, shallower hole. I've seen forged crank big blocks that were just pre-drilled, but weren't big enough or deep enough to accept a pilot bushing.

I think they switched to cast cranks in 1973, and doubt that they were drilled for a pilot bushings. I could be wrong, but I don't remember ever seeing a cast crank drilled for a pilot bushing.