Head scratching wiring

New to StangNet here, hope yall can help me out. I have an 86 gt that I have owned for 8 years and is mechanically stock. It sat for about a year and when I took it for a drive, the starter engaged on its own while the car was under power. I pulled over and had to pull the battery cables to make it stop. During my troubleshooting, it was found that power was going straight to ground. I have chased the problem to the circuit that controls the interior lights, digital clock, and somehow the headlights. There are no rodent chews in the wiring and I am now to the point of pounding my head into a wall. Is it possible for the jamb switches to wig out and cause this. Any advice will be greatly appreciated.
 
There is possibly a ground wire missing or has become corroded.
There is possibly a ground wire missing or has become corroded.
follow the burnt wires, could possibly be the light switches in the door jamb. Check out veryuseful.com for wiring diagrams.[/follow the burnt wires, could possibly be the light switches in the door jamb. Check out veryuseful.com for wiring diagrams.