The good news is repops of the connector plastics are available. I have seen these on ebay, and i believe Pico wiring is the one who sells the packard 56 male and female terminals in the larger wire gage for the heavy ammeter bulkhead wires, and in the smaller sizes for the other wires. The reason i say that, is my local electronics store sells em in packs of 10 male or female, i think their supplier for these is pico wiring.
I also was able to get a large size full color and laminated schematic of my 67 cuda wiring off ebay for about $18 This has helped a lot.
Looks like that may be your ammeter wire that melted. You need to concider disconnecting the ammeter and doing the ammeter bypass wiring modification. I did this, and put in a volt gage.