took a screw with me. I still wasn't convinced that it was 8-32 ...just didn't look like it. But I finally was convinced by the guy at HD. Bought a tap, tried it in a piece of scrap, using one of the old screws and it looks like it should work fine. Right now i have a c-clamp holding the fourth corner of the valve. So at least we have the boiler running. tomorrow surgery will begin.