Get a wiring diagram at mymopar.com then go back and visit what you did. If it worked before then it should work again. Sounds like you mixed up some wires or messed up some wires.
If your harness got hot when the amp gauge melted down then you may have wires in the harness that have insulation melted and they are touching each other.
Yes, I have had this happen on a 68 cuda, and when it did the wipers came on without the switch on, the radio power and the dash lights also. WITH THE KEY OFF! Also it would start but not stay running.
I un-taped the wiring harness where it had gone through the ammeter and low and behold several wires and the black hot lead had fused together causing the circuits to be fed hot all the time.
If you got hot and melty then look there first.
Good luck.
