what size carb do i need?

If you add up all the 2-cents worth answers you get, you may end up with half-a-buck! My 2-cents also says go with an 850cfm carb on this combo. I ran a highly modified 340 on the street years ago in SoCal and a Holley 750dp couldn't keep it fed. Had to go to an 850dp to keep from running out of fuel on the top end.