Justhorsenround.......Well, this is a truly bizarre case in my opinion. I have gotten alot of great suggestions, but so far the case is not cracked yet.
I agree with you that a refurbished starter could have issues. But the wierd thing is that the old starter was giving the exact same symptons as the new starter.
Since engine heat seems to be the cause of the problem, I just need to do more testing and try other things, like mounting a Ford solenoid far from the starter. Another idea is to run a longer heavy gauge copper wire totally away from the headers.....route it along the wheel well and down and then up to the starter. If this works, then maybe its just way too much heat too close to the battery cable running to the starter.
Old time Alternator shop....I think those have been disappearing and moving to China. All we can do locally is to lay it on the counter of an Advance Auto and ask them to test it. (By the way, the old battery that I took out a few months ago.....they tested it and said it was fine. I bought a new one anyway).
Or could it be those UFOs that have been hovering over my house the past year?
Another thought: Anyone wanna buy a fine 69 Chevy C10?