The vehicle is a 1951 Chevy 3600. And yes to the guesses, it was an original wire from the ignition switch, and agree that it likely some wearing took place to a point where it arced to the dash brace metal. To get through the Minnesota winter I'll replace that wire, then next summer replace with complete wiring harness. I was looking to do a wiring harness replacement anyway. There's just a bit more incentive now. While I'm under there I'll look for any other rub points on any remaining original wire. THANK YOU!