Aha....The 40 yr old gauge letting us down again.. How rare. Lol
Glad you found the problem.
Sounds like it is time for a new starter. Look into a mini starter. They work much better.
just sharing info: a quote from the very first post in this thread
"The motor does not crank when it is hot, i have a mopar mini starter on it."
I cannot stand Mini Starters, to me they are all expensive junk!!! IF I was given one I would throw it away. cannot see burdening someone else with junk like that!! IF you at all can replace that mini starter with a full sized SHORT Mopar starter...chances are your car will start hot or cold, unless your headers touch the starter, THAT can be an issue