years ago I had a ign coil short to ground. It caused the alt to charge like a sumbich. Just something to check if you have a spare coil. Btw the car ran fine.
Couldn't possibly run if the coil was grounded. You'd get no spark.
To the OP, the biggest culpret in these older cars is resistance cause by poor electrical connections &/or bad grounds. The bulkhead connectors are a usual suspect, but cleaning isn't enough. Make sure the pins fit snugly into each other & the wires are attached to the pins firmly. And clean doesn't mean spray & wipe clean. It means shiny metal clean! Go through every connector in the circuit & make sure they're good.
