My alternator / battery light came on one day while driving.

I was nearby, so I drove to my in-law's house (50 miles from home) and later measured battery voltage while engine was off: 12.6V
Start the truck and the battery voltage DROPPED to 11V, and would not increase as I revved the engine

I left the truck there while I sourced a new alternator.

Dealer list $950.00
Dealer parts guy wholesale 'hook-up': $752
WOW! At those prices, I was now fully prepared to take the thing apart myself or take it an old alternator shop in town and try my luck.

Anyway, some internet searching led me to novastarparts.com They rebuild alternators and starters in bulk for emergency fleet vehicles and others.

Price CANNOT be beat: $171.45 !!!