Not 100% sure on the alternator, this truck is new to me as of last spring, right when we all quit driving anywhere. Suspect original, though, truck's got ~240k on it.
0V...might be the regulator. I think it's built in to the alternator.
If it isn't your primary/daily, I'd start by pulling the alternator. If it's OEM, it might be worth rebuilding. If it's already been replaced with a parts store reman, then...just do that again.