Rumor had it that some engines came from the factory with up to 0.040 misalignment. Others have said that you shouldn't swap belhousings between blocks. I have done lots of swapping without problem. Maybe I'm lucky.
I have heard that there were/are offset dowels for just this purpose but the manual quotations indicate that the tech writers were unaware of that if they really existed. One indication of misalignmet would be shortened clutch-gear bearing life in the transmission. I have not seen this problem though.
