Melted ground wire

Dana67Dart said
As for why did your ground wire melt...

It became a fuse.

It did not have sufficient current carrying capacity for the load being pulled.

10 gauge is not all that big, typically the ground straps are branded copper straps.

It would not hurt to add additional ground to body straps.

Without them you could be using your transmission and linkage or another path to ground.

Understood, i will add one at firewall but based on voltmeter clarification. I definitely am seeing like 24.5 v in 200 dc (flat line w/ dashed line under it in black) and 13.5v in 20 on this 72 cuda and my 69 barracuda is 13.5/13.50 in both settings. Something is off there that I can’t wrap my head around