While finding and cleaning more grounds, I discovered that my original starter ground was a nasty cable, with a few breaks in the sheathing along with very few copper strands still connected. The cable was in a pinch-clip that was tack welded to the frame. I opted to replace it with a more modern cable and came up with a new connection style.
In the below pics I show how I ground the original grounding area, then welded a bolt to it. This allows me to use a pretty standard cable from the starter bolt to the frame. I covered the whole setup with fresh undercoating.
Posting just for fun. May give someone else ideas.
