From what little i know, you just have to make sure the throttle spindle and float bowl seal well. Then run a line to the float bowl vent. SU's are pretty well sealed anyways and fairly easy to use for blow through. On webers and holleys they usually just slam the whole carb in an airtight container. The MG Maestro turbo had SU carbs from the factory and i believe it was a blow through setup...could be wrong tho.
Found this tuning guide when messing around with researching carbs; http://www.turbominis.co.uk/forums/inde ... tid=159683
Might help you?