My father had a saying- - - -"Getting repair work at a service station is like getting brain surgery at a drug store!" In the same general train of thought, getting electrical diagnosis from some computer jockey at a parts store makes just as much sense. Find someone who can follow a wiring diagram and see if all the circuits are intact. Use a wiring diagram for a late-1960's or early 1970's GM vehicle with the "Delcotron" external-regulated alternator, and duplicate the circuits exactly.

Converting to an internal-regulated 10-SI alternator would be a far better choice.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!