The powerheads are just stock E7 heads that have been sent out to be ported by some company that I forget the name of. Only way to tell is to pull the intake or one of the headers and look at the ports.
A friend of mine had a set that came on his supercharged mustang. He took them off and replaced them not knowing what they really were. The looked nice for stock heads. Ported to the max. You could get a good idea by looking at the ports if they were powerheads. The ports will be smooooooooooth and massive!
^That's actually pretty impressive for a stock head. But IIRC they charge like 800+ for the work and it's still a heavier head and flows less than a used set of TW's that flow 240 box stock that you can get fot the same price. If you already have them, cool. Never spend the money on it being done tho.