Pilot bearing
Make sure that the input shaft doesn't bottom out in the back of the crankshaft. Some truck cranks aren't drilled as deep. Meaning.... don't force the two together by tightening the bolts. They should go together without a ton of force.
If they don't.... I had to trim about 1/8" off my input shaft (alum 5.3) and put a bevel back on the end. Solved that issue.
Also a GTO bellhousing will need some clearancing to run an Fbody or truck starter where the snout goes in. Just makes a mess.... but needs to be done unless you run the GTO starter ($$$).





