I had my 440 Source Stealth heads milled. 050" to raise the compression. One thing I learned is that on big block Chryslers you mill the intake surface of the heads instead of milling the intake itself. One of the engine builders here on FABO told me about it and it makes good sense. This way you don't wind up with an intake that only fits one engine. The formula is: Take the amount milled off of the combustion chamber side and multiply that number by 123% and then take that off of the intake surface on the heads. Lets say you mill the heads. .050 . .050x 123%= .0615, so take. 0615 off the intake and an un modified intake fits good. It cost me $250 to mill my heads. Thats worth it to me. A nice bump in compression and I can try a bunch of different intakes.