Great you nailed it down. I think you have two options. Refurbish the generator by yourself, there are lots of vids out there. I would do that if you have time. Otherwise buy an excahnge unit and resend you old alternator. For dissambly check this.

I'm leaning towards replacing just the pulley and hoping that solves the noise issue. Are there other parts of the alternator that might be making the noise, or is it likely that replacing the pulley will solve it?

If the car is a manual transmission, the alternator will have an OAP (overrunning alternator pulley has a one-way clutch allowing the alternator to coast freely), if it is a Tip trans, it will have a simple fixed pulley. The OAP can develop noise, the simple pulley will not. There are also bearings internal to the alternator which can go bad as well.

Turns out it was the alternator. Guess how I found out?

Lesson 1, don't wait too long once you hear the rumbling. :)

https://cimg9.ibsrv.net/gimg/rennlis...7d9aae961a.jpg


Lesson 2, don't skimp on an eBay alternator as a replacement. I should probably be glad that it broke before I got it installed in the car.

https://cimg1.ibsrv.net/gimg/rennlis...a6030058cf.jpg

Ended up buying a new Bosch and everything is working amazingly. Thanks so much to everyone here for helping me navigate this problem from start to finish!

This is what I use, it provides charging possibility and gives you the information from the alternator. Can be switched off.
https://external-content.duckduckgo....2515601d745832