I agree... should stick close to stock jetting for a start and move from there. Being over-carbed "shouldn't" affect the a/f but the throttle response won't be as crisp... I don't think the 750 on this 383 is overkill but a 650 would probably give better response (though the vac secondaries should help this situation...)

Disclaimer: I've been proven wrong more than I care to admit!

Two cents,

-Chris