There are many levers to play with, in addition to BB axle length, you can offset the BB is the frame by using a spacer between the frame and the BB. Conveniently for BSA threaded BB, freewheel spacers, cassette spacers and BB spacers are the same. A bag of these comes in very handy: https://www.amazon.com/Wheels-Manufa.../dp/B0025UINFC