Grit Dog, when time permits I have had good luck (with the limited parts I do buy) buying stuff at Rock Auto. Out of curiosity I looked up a 2001 Tahoe with 5.3. They list 14 alternators as "new" (take that for what it's worth) and another 13 as "remanufactured". I think I would roll the dice on "new", either AC Delco, Remy, or Bosch on what they list if I needed an alternator.
A lot of times you can cross reference those by part number to other places such as Jeg's or Summit and beat the **** out of their prices, just did that on Powerstop drilled and slotted rotors for my GMC. Free shipping and a SANTA discount code.
My BIL had his own shop and just retired after 35 years. He was always butting heads with Autozone, Advance, Napa, and some others over garbage parts they would send him, including some of the big 3 dealer parts departments. A crapshoot at best.