I think we need a picture of the crankshaft extension (the PTO) where it emerges from the crankcase. It is common for there to be a build-up of hard crud there, which won't pass through the main bearing bore. However if this is on an SB45 it is also not rare for a previous tenant to have put a sleeve over the PTO to keep the clutch from sliding toward the engine. If that has been done, you need to take the sleeve off first. So, pictures please.
