Hey Pops, I don't know about the '78 750A, but the twin piston calipers will bolt right onto a '77-78 750F with Comstars, with the correct bracket. Does the 'wing have a hydraulic clutch? If so, what is the diameter of the master cylinder piston?
Bill had a strong left-hand actuated rear brake on the Samauto, but I don't recall what parts he used, or how high they could rev the motor without creeping.
Scott