Another alternator problem
Maybe the odds are better or maybe you have just been lucky. I've been through a few 12SI in my wagoneer. Feb 2019 made the last hour and a half back into town on battery alone thanks to the junk output stud insulator and lack of QC - from a AC Delco with GM numbers on the box. All rebuilds, remans, etc are a crap shoot.
Years ago I rarely used electrical stuff from a junkyard. Now, if its original and in OK condition, its my first choice.
Here's the insulator. That's not loose! Junk.
This was exchanged for an older AC Delco 'rebuild' which did not have that issue. Yes I opened up and checked it out. Had to clock it anyway.