Well as for the carb, i talked to the guys at BG and they said that the 825 mighty demon will flow 930 cfm. If you look at the specs between an 825 and an 850 they use the same base plate, but the 850 has a slightly bigger venturi. BG said this carb would be fine unless i tried to use it on a 496, then it would become a bottleneck.

I will however make sure my engine builder has an 850 or 950 Holley on nand when we dyno so i can see if there there is a big choke on the motor?