The connections honestly aren’t that bad. That was the one part of that section that wasn’t melted. The wires were fine from about 6 inches out from the bulkhead. The connecters actually look good. I can pull them apart and clean them? Possibly re-solder them?
I think wire is covered in the Chrysler Connector thread.
Under the dash, automotive primary is fine.
For hot, fuel, oil or salt and moisture, marine grade or SAE TXL, SXL or GXL should be considered.
Marine supply often have a wide variety of insulation colors and will sell by the foot. or maybe in BC by the decimeter.
Rhode Island Wire has a lots of insulation options.