I know Mr. Kunkel has forgotten more than I will know about the 727, but I just installed a new beville spring in my trans. I have the old piston and beville. I bought a “new” part number piston and compared it to my old piston. They were the same height. From reading everything I could find this is what I think happened. I think chry reverted back to the old piston height, but just used the same part number while adding a letter to the number. I have read that people would order the new style piston and it would be shorter sometimes. In that case they blamed improper machining, but I think there are three possibilities. Old style,new style and new part number machined to the old style hieght. I have read John Cope say they went back to the old style beville/piston in the newer trans. I have also read they add a letter to a part number when they supersede it. Again I am NO expert!