Exactly!!
You have to match things up to make it work right. If the heads are ported to flow 270cfm they'll make the 500 hp he wants but to make that kind of horsepower he'll need a really big cam, at least a 750 carb, and a single plane intake, and it sure ain't gonna be very torquey down low and work well with them 3.55 gears. Tell him he needs to think more in the lines of 400-425 hp if he wants good low end torque and something to work with those gears. I'd say have him call Jim at Racer Brown and tell him what he has and what he wants to do and he'll suggest his best options. His # is 410-866-7660 and you can catch him after 2 pm eastern time.