If you have your heart set on a triple and you have lots of Stromberg BX parts, then you may want to look into the older BXV carb (which was standard equipment on the '39 and '40 Stude's). The 'O' in BXOV is stands for oversize throttle barrel - by an 1/8". The smaller throat might help in keeping velocities up on a triple. I think some of the parts are interchangeable between the BXV and BXOV.


[Linked Image from 49fastback.com]