Grinta wrotequick reply and the answer on my own question: strada/SP frames have a different lockstop than the racing frames. That's why the racing stem is 5mm shorter!
The MG lower yoke I have has a flat top surface, and hence matches the flat lock stop on the race frame. ( no need for clearance )
The strada / sp lower yoke has clearens for the thicker lockstop on the strada/sp frame (teeth)
The conical bearing seats are in the same position in both frame types..hence it all about the thickness of your top and bottom yokes.
It quite easy to convert the strada/sp frames simply cut off the teeth. (The Flat topsided MG yokes does not go on a strada frame with out taking off the teeth on the lock stop)
