73 Dart Electrical connector

That is a engine harness connector. It was added for the assembly line. To delete the thing may be a better plan. Moisture causes corosion, corosion causes resistance, resistance causes heat. Tinned terminals and some sealant or silicone moisture barrier would have helped but... Anyway, what else would cause the melt ?
There is a little ceramic box mounted with your coil bolt that controls a electric choke assist. I would bet that thing is shorted inside. The moisture got in there too.
It can be deleted also since it isn't required.