In my days I was always told that a smaller carb that runs 85-90% efficient is better than a bigger carb that runs 60% efficient. I always had good luck with the 750 double pumper in the 70's on my LT-1 nova. That carb seemed to run better out of the box than the 780 I started with that had small modifications. I also was under the impression (from the guys who ran it) that the 3 barrel Holley was a bust. At least in the early days it was. Racers would put it on their LS 6 chevelles and slow it up in both et and mph. But like I said this was the 70's.