Here's the way I feel that this works, like it or not, a larger engine will always pump more air and make more horsepower. I know it's frictional loses are slightly higher but it's going to pump more air no matter how restrictive the cylinder head. How is this possible? Doesn't the port saturate more quickly on a large engine? Yes...
But, think about this for a minute... Lets say that a smaller engine with a given cylinder head forces the head to flow at it's maximum for a short period of time during the induction cycle at high rpm. Every cycle it goes up and then essentially clips the top of the flow curve, flattens it out on top. The valve opens, the engine pulls on the port, flow increases up to a point where it levels out. Now we take the same head and put it on a larger short block. What happens? The valve opens the amount of flow goes up and maxes out at the same level as before, pretty much. BUT, it gets to that maxed out point more quickly because the engine pulls harder on the port, thus it spends more time flowing at it's maximum than with the smaller engine. The demand is greater so it gets it moving more quickly and it holds it there for a longer period, pumps more air and makes more power.
Remember the test we did on the dyno using Shannon's 460 with a tech legal 4412 two barrel. That carburetor has never made more than about 400 horsepower on my dyno while running on a 355 inch engine with a cam that's pretty optimized, high 14:1 compression etc. Just bolting it onto a 460 with 11.8:1 compression it put out 25 more horsepower! How can it do that?
Now I know that gaining 25 horsepower by adding 100 cid isn't dramatic but 25 horsepower IS 25 horsepower and that means that the big engine will go faster than the smaller one even with the little carburetor, about 6 inches of mercury in the intake at wide open throttle and a power peak at about 5500rpm. Remember too, a 4412 is rated at 500cfm but it's only 50% as big as a 750! A fun and interesting test don't you think?