How much power from intake swap?

What are the rules concerning plenum top height and or carb spacer height? The design you have now will not work very well. You need to get that carb higher and make a much better transition into the runners. As it is now I bet your plenum volume is too small, that combined with the challenge of feeding the outer runners will result in less than the desired outcome. As some have suggested a split Dom would be your best 4 barrel. Is it legal? J.Rob