I'm new here and have a newly rebuilt speedmaster II drive and need to find a parts manual, maintenance etc
Plan on coupling this to a new Merlin block 500 hp
any suggestions would be helpful

Check Ebay

thank you, hope I found the right one

If your SSM II is a good working unit, you would be better off to sell it. They were not very strong, infact many were replaced with TRS (same upper, 1" shorter) as the TRS lower was stronger than the SSMII. Parts are extinct and would not last very long behind 500 hp BBC.