On both my '82s, there is a grounding strap from the firewall to the back of the driver's side head. It's about 13-14 inches long. Dorman 60213 is a very, very close match. You might be missing this strap.
That strap fried on my chassis. I got a replacement for it then added two more grounds. Welding cable ground from chassis to starter motor bolt and same cable from chassis to rear of passenger head