1983 dodge d150 overcharged battery

I don't remember if an 83 pu has a "full current" ammeter or not. First thing to do is find some way--mirror, camera, small child, LOL and look up in the cluster and see if there is the usual "big red" and "big black" or not.

I've recommended relays for years, cut the "run" wire coming into the engine bay, use the firewall end to fire a relay, feed the relay off the starter relay with a breaker/ fuse, and connect engine bay end of the run wire to the switched contact.