IMO. You want big power but your choking it with the heads. (IQ52, agree)
That's a street replacement head. Not a racing head. (IQ52, agree)
To really make that kind of power (675 hp) your going to need at least 350 cfm of flow on the intake. (IQ52, disagree)
With what you have it will fall off around 6200 rpm. (IQ52, or flatten out, so, agree)
It dosen't matter how high you lift it. If you lift it past the maximum point of flow the flow falls off. (IQ52, Yes, but what effect does that have on the horsepower?)
Your looking at around 520-550 hp IMO. (IQ52, disagree, already proven not true, eh J.Rob?)