Even though the heads dont flow at that high of lift, it still can benefit from the extra lift. If you think about the ramp on a big lift cam it opens the valve faster and the head spends more time at its stall and you end up with more power. Even a stock lift head will make more power with a .590 lift cam will work on a stock port that stops flowing in the .450 lift range. Just my 2 cents from my experience.
