Blowing Voltage Regulators

My buddy has a '63 Dodge 440 (stock 383, 4-bbl, auto, A/C). He's had to replace 4 or 5 Voltage Regulators (both mechanical & electronic styles) in the last 3 years. The car works fine during daytime use. Once he turns on the headlamps the car drives using the battery until it is depleted. He replaced the alternator and the voltage regulator and was good until the next time he used the headlamps. We put the headlamps on relays, installed another voltage regulator and had the alternator bench tested (by a gentleman (Marv) that has been rebuilding starters/alternators for 40+ years). Again all good until the headlamps were turned on. My buddy took the car to Marv to have him identify the problem. Marv put a 12 gauge wire (with a 16 gauge fuse link) from the starter relay B+ lug to an ammeter connection on the bulk head connector. Marv said that'll do it. Well again the headlamps caused the voltage regulator to blow and leaving the car driving on the battery until it was depleted. My buddy is about to throw in the towel.

I keep telling my buddy we need to bypass the bulkhead connections as well as the ammeter (like MAD Electrical Bypass). I've tried to explain that the wiring (when new) was barely adequate to do what was asked of it. Now that the wiring is 55+ years old and exposed to the elements and that the bulkhead is not a "sealed" connector I'm sure there is corrosion well down the wire.

BTW we've also had two batteries load tested and installed.

Is there something I'm overlooking?