Ok conductor I am going to take a stab at this and I am sure if I am wrong one of the many guru's here will correct me. If you actually have a 261 you should have a set of Captain bars "II" cast into the block ( I believe on the drivers side down near the back). Also the oil lines should be 3/4" pipe thread ( yes this is big). There may be additional ways to id this engine but these are the only ways I know without tearing into the engine itself. Good luck and I am sure someone will post the link to Jim Carter's page about 261's if not go to the link section and search his site.


Brian Moore
1949 3100 5 window Deluxe
"Today is better than yesterday, but not as good as tomorrow"