What size carb?

^ What he said.

Is your Holley 650 a Spreadbore or SquareBore?..the easy way to tell is the Secondaries have larger Venturi's on a Spreadbore....squarebores have the same size venturi's on all corners.

650cfm is fine for up to a 450hp small block...although above 450 crank hp, your gonna need more fuel/air...and a 750 would be desirable then.