Squealing fan belt driving me CRAZY

[drealbmw]

Three weeks ago, my brother became the proud owner of a 1930 Model A for the first time. So everything on this old car is new to us.



It's a beautiful car, but we have a problem: fan belt squeal. In fact, the problem is so bad that he asked me for help.

The mystery began when we tried a new belt. The noise stopped, but the alternator stopped charging, too. In fact, it started discharging!

After 4 days of fiddling, we found that:

1) A new 1/2" belt stopped the noise, but the alternator no longer charged.

2) A new 5/8" belt charged the alternator, but the squealing was unbearable. If we thought the noise was bad at idle, when we turned on the lights and the a/c, the noise became 100 times worse.

We have tried everything:

1) New belts
2) New alternators
3) Soap
4) WD-40
5) Dressing
6) Circuit tracing

Now we are considering a mismatch of pulleys. Is that even a thing?

The crankshaft pulley looks like it was made for a 1/2" fan belt. The alternator pulley looks like it was made for a wider belt, such as 5/8".

We even made a clay/putty cast of the two pulleys to see if we could find a difference. We did. You can see it on this YouTube video:

https://www.youtube.com/watch?v=wlhYWdAN0Ak

We will appreciate any and all help about what to do next. We're running out of ideas.