My old '79 F350 with a 460 was equipped with, I believe, a 500-525 cfm OEM Holley carb and until it just plan wore out at the shaft, worked just fine. I replaced it with a 600 cfm Edelbrock Performer which was fine as well and actually gave me a mpg+ better gas mileage. Big isn't always the way to go - that is unless you either need braggin' rights or are racing it 100% of the time.