My 650 Holley DP seems to be perfect for my combo. XE274 cam, AirGap, stock X heads, 3.91 gears, 3,500# car runs high 12's with the 650.

Everyone said it would run quicker with a Holley 750, we put one on and the car slowed down 3 tenths, even with tuning. Swapped the 650 back on and the car jumped right back.