I use the KB quench pad pistons in the 440 thats in my 63. I also use 906 open chamber heads. You have to measure every chamber and piston pad height and work them as my quench pads varied from .054 to .057 above the deck and the head chambers varied from .038 to .032. So I had to work them some to get all my cylinder's quench betwen .040 and .045. But it works good as I can run 92 pump and 38 total timing with no ping at all. I estimate my flywheel HP to be right around 500 by my 3700 lbs and my 1/4 mph. Ron