Update: I spent the day ripping apart melted wires. I took the steering column and cluster out completely allowing me free access. Someone had mentioned a fuseable link. The fuseable link at the starter relay was still intact but the wire was melted. Bizarre.

Red and Black were the cooked wires. The others around it were collateral damage with red and black melted goo on it but they are still intact. As I took the time to peel them carefully apart, I inspected the other wires and so far so good.

I was hoping to try to replace just the black and red wires for now and see if that would work. Being an original harness, I wonder if those two wires had somehow worn and shorted within the harness? The red wire is completely out, but the black appears to be spliced to several other circuits so I will just cut and splice the new ends (see photo).

Could the ammeter be had causing this? If so, how do I test it before I put it all back together?