Looks super simple to me?
That BATTERY TERMINAL on the FIREWALL is the "cause". The fire was the "effect".
Based on those pictures alone, it
appears that the OE fusible link at that location has been substituted for a ******* battery terminal thus effectively defeating the inherent safety feature of a FUSIBLE LINK that the General so wisely had installed there.
My money is in the starter solenoid but you must repair the damaged wiring, first.
When you try to start it again , if it doesn't wanna turn on just whack it with a hammer a couple of times - pretty good..the starter.. If it starts right after super easy, that's the problem. If not- we'll have to look at BATTERY CABLES.
That trouble ain't a mystery but you've got some work to do. Those melted wire looms must.be. separated and the wires repaired INDIVIDUALLY.
Pain in the ass!
Ready?
Go!