60-66 full body wiring

[thefaceman]

New here and to the c/10 world, so sorry for dumb question, but I noticed a puff of smoke come from under the dash a couple days ago, and jiggling the wires behind the ignition switch shuts the engine off. The truck was re-wired by a shop before I bought it. I don't know what kit they used. It looks like some wires are getting hot back there (I have reached down and touched them, and the area where they attach to the harness behind the ignition switch shows plastic is melted a little). I feel like I could label, then pull wires and fix loose connections, but I don't want to mess anything up. I also will need a new harness for the back of the ignition switch. Any thoughts on how I should approach this? How should I go about buying a harness without knowing the type of wiring kit used? The ignition switch itself looks like the original. Thanks!

1966 c/10