The top bolt came out with lots of noise and some case threads due to corrosion or galling. It was able to go back, and I used lots of anti-seize.
Now, 9 years later I heard a single click once starting(and it always starts strong) and wonder if it will come out again without breaking.
Leads look ok at the solenoid(visually), and at the relay(cleaned those), and my battery terminals are always shiny but to really test/inspect the starter end the starter has to come off. Parts store tester said everything is ok, but they can't really tell if you have a dead spot in the starter.
I would probably change the fender relay if it happens again, even if I'm not sure its that. I had those fail in the past on other fords. 20 years is pushing it.