I post this in case it's useful for anyone else with this problem. I posted earlier about the ring gear slipping on the flywheel to which it is attached by friction fit.
The ring gear was not cracked or damaged in any way. So, usually this means a new flywheel. Hard to find it seems. So, I took the ring gear and flywheel to a welder and the welded the ring gear to the flywheel along the leading edge where they meet then ground the weld down to make sure it would not interfere.
It's installed now and works like a charm. Thanks for the ideas from several of you for dealing with this. I hope this helps someone in future. Steve