Overcharging problems

This has GOT to be a voltage drop problem. If you can duplicate operation under a fairly heavy load, or maybe just jumper the fan to run for a period while you are measuring, chase the VR IGN wire through it's terminals to the ignition switch and back to the battery. The blue. You might find drop EG on both sides of the bulkhead connector. You might find drop between the terminals of the ignition switch. If so, one way around it is to activate a relay out in the engine bay by cutting the blue and feeding it to trigger the relay. Feed the relay contacts power from the start relay "big stud." Hook the other end (engine bay end) of the blue to the switched contact of the relay.