SUCCESS! I put the disc valve where it belongs, put the new gasket and diaphram in, sealed it up and pressure checked as instructed. A few bubbles showed up but quickly went away with the tightening of 2 bolts. I should have replaced the old slotted head bolts for some that you could put a socket on. I still might. They were almost impossible to get off. I hooked up the tank to my '59 5.5 Jubilee and she started right up...and stayed running, something it wouldn't do before. Many thanks to all that helped me. Hopefully I can get the impeller changed out next, with everyones help I'm sure. I'm taking her to the lake tomorrow, supposed to be in the 80's.