Battery voltage drop

Glad you fixed it. 67Dart273 has answered this question a gazillion times, so search his posts (many photos). Keep the square-back alternator since better and easier to repair. It might help to clean up the ground connection on your Vreg (the sometimes rusty sheet-metal screws).

If your dash ammeter works, that is a great way to monitor the charging system. A slight discharge at idle is OK, as long as it goes positive after starting and at higher rpm. I also use a cigarette lighter voltmeter in all my cars (Amazon, real cheap LED one at HF). My newer cars have you flying blind and when the battery gets low, they go crazy. In my 2002 T&C, when the serpentine belt was slipping, I knew the battery was low when the windshield wipers started actuating on their own, the electronic transmission display started showing all gears, chimes going off, total car voodoo. Started using a voltmeter on trips since then.