I can tell you my 906 iron headed 440 in my 63 came out to 10.0 comp after I used the right head gasket with the 906 heads. I run 38 total timing all in by 2000 rpm and I use the MP .557 cam. It runs great on 92 pump with no ping at all. I do use the quench pad pistons from KB as I got the quench on all cylinders in the .040 to .045 area. But it is nice to drive to the track and stop along the way to get pump gas in the 2 to 3 dollar range and not have to get race gas at the track for 8 bucks or so ! I figured if I ran 11.5 or 12.0 comp it would only be worth a tenth or two and its not worth it to me as I will give up a tenth or two to save money as I never have enough money now as it is. Ron