'83 D150 overcharge

You've been given good diagnostic advice so far and it’s nice to see you following it. I’ll add only one thing I haven’t seen suggested yet. @67Dart273 briefly touched on it in post 11 but it was an only a brief statement. Before you do anything else, make sure the VR is cleanly grounded to the body. Remove it, sand the body to bare metal at the contact points, and re install it with star lock washers. It’s also necessary some times to run a ground wire directly to the battery neg from a mounting bolt on the VR. It HAS to have a good clean ground.