Yes, 276 is correct pre 54, I think.
I just love the design & appearance of the 276's, all the nice parts in there

, would not like to change for a 376. My 276 is perfect, but unfortunately 15\16, should be 1 1\16, so I do not have full power at full throttle, probably ok regarding riding too fast or wearing out the engine.
Also see my posts in
http://www.audioworld.net/BSA/forum/index.php?topic=90.0 E.