Re: Which Carb?
IMHO the only time a 750 would be better is at full throttle. The primaries are much smaller on your 600 and it's street manners will be much better. This is why Quadrajets were used so often on stock engines. I would look into an electric choke for your Carter and keep it.
69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1