Very interesting, thanks Iowaboy! What you mention is the very odd way that electrical issues can show themself and seem impossible to solve.
I forwarded this to my brother and uncle. Next step if my brother is willing is get a service manual that walks us through checking the ignition and charging systems.
The motor runs ok but doesn’t start or idle as well as it could, especially when it was colder out. Wouldn’t be surprised if whatever the issue is would help the motor run better and give solid readings at the same time.