I have them in my 63. It is a stock bottom end 440 with .030 over KB quench pad pistons. I have 906 heads and as was said the head chambers were not all the same and I had to do some work with them to get them close. Also with recon rods my quench pads varied about .003 difference above the deck. But I have between .040 to .045 quench on all my cylinders. It works good as I use the MP .557 cam and have it at 10.0 comp. It runs fine on 92 pump with 38 total timing. Its really a mild 440 but will push my 3700 lb 63 street car to mid 11's on 92 pump. Ron