Pat, from what I have read online (I know not always good/correct info) and my own research the heads I have would not work with normal open chamber pistons. I could be wrong, but that was the conclusion I came to and that is why I am having BME do the pistons. He just scanned my old Ross pistons and is making the new ones to the new bore size 4.580. I could not find many shelf pistons in that bore size, summit has some JE in that size and the price of those compared to the BME would of been pretty close. In fact we are going to use the JE rings because it was hard to find rings for the bore size. I also went with BME because it is nice to do business face to face and like to support local businesses when possible.