Well for a few dollars more you could buy a porting kit, a die grinder and a few bits for the grinder and do your own heads. Just removing the EGR bumps and opening up the roof of the exhaust ports then matching them, to your headers will make a big difference, in letting them breathe. You will also make headway by blending the bowls under the valves, and port matching the intake sides along with removing any sharp edges in the ports. Total cost of this would be less than $100. Or shop around for a set of E7's or early 351W heads that someone else is selling that are already done. You could pickup a set for anywhere from $200-300 or maybe less if you're patient.