Overcharging Problem

Ditto above, problem in the wiring harness or bulkhead connector. The VR falsely senses the battery too low (via key switch) and applies full-field to the alternator. My question is why are your VR's failing. It should be able to run the field full blast all day long.

Are you using an original VR (for round-back alt) with a newer alt (square back)? If so, you can get a modern electronic VR that fits in place of your original one (same connectors). I got a thin chrome one for ~$11 (rockauto I recall). I expect it will work fine with a squareback alt. For more money, I understand you can get one that looks like your bigger black box VR, but electronic.