Not charging HEI upgraded:

Give us a photo of the alternator. Is this a Mopar unit? 1 or 2 field connections? (The small blade "push on" connector(s)

Might be it was never wired up, for all we know you have a "one wire" setup of some sort. There IS an add on small unit for Mopar "most any other" alternator a little "bug" mounts on the alternator
Correct!