I would check the BATT wire along the VC looking to see if it has a factory plug or it runs all the way over to wheel well area.

when i striped the 85 harness for the 88 440 truck I swaped the 88 BAT wire over to that harness to ditch the plug like my SB 85 had.. which is the trouble I had over charging burning up alt/VR.

glad you found the bad wire at the VR plug,i have replaced those be for for the same reason.