I have a guy getting my 71 SS up to speed rebuilding carb, valve gaskets, new points, dist (laughingly said it still had the original distributor on it)and he said if I put a Holley 4 barrel on it it would run like a squalded dog as the Rochester is vacuum controlled and doesn't really act like a true 4 barrel. I have no clue so I thought I would throw it out on the board. I'm keeping the original anyway as the whole car remains original but could always swap carbs if it's that big a difference. Thanks all.