I'd like to have put this simple 440W9 Bracket combo on a DTS dyno.... Should make about 870 based on what I've seen (10% more) If it had more cam in it (was 274 @ .050) probably had bit left in it as well. So with different cam, carb & little more tune time, I bet it would tickle 900 on a typical DTS.

I think same motor with good set of Cup P7's on it "should" be 60-70 better. I think a 476ish inch type P7 with between 14-16:1 & big roller will make around 1000 on a "normal" dyno. Biggest thing limiting the P7 for use on big CID & making massive HP is the intake valve size... Yeah they flow alot, & have alot of cross section, but the throat area & valve curtain area is the #1 limiting factor. Most of those heads are 2.20" valve deal....