if you cant get it to charge or need to rebuild it or replace parts you may want to look at swapping it for an alternator. they charge better and probably have more output. if you have more than lights and a fan operating the generator is gonna be overtaxed likely. an altenator will keep up better. if you are going with a numbers matching redo or want a totally stock truck then it will be what it is. adequate if bone stock and operating properly.
here isa thread on the alternator swap and how it's wired. I did a swap on a buddies '54 and he hasn't looked back. waaay better.
https://67-72chevytrucks.com/vboard/...d.php?t=783739
and another
https://smithcoelectric.com/blogs/te...wiring-diagram
and one on polarizing the gm generator from that era
https://www.motortrend.com/features/...962-corvettes/
hope that helps