Well, I have answers to a few questions I guess. Neither answer is what I wanted to hear, but that's par for the course for me.
1. I think I know why my gas gauge never worked.
2. Undoubtedly need a new tank.
Time to break the bank with a new tank, new sending unit, and probably the filler tube grommet. Ugh... $$$
My collar tool ended up being a Valley Forge Flag Co. product. Bottom edge fit nicely across two tangs.
