B31 or B33 top end?

[Janacek]

Is it possible to tell lf a B31 has a B33 top end without taking the head off to measure the bore?

[Derek996]

The only obvious thing I can think off is the carburettor size. 1" on the B31 and 1 ⅛" for the B33. Although strictly speaking best to check the inlet port size as the carb might have been changed.