2 alternator/fan belts shredded...why?!

[indybenz]

Greetings fellow afficionados.

So I've had 2 belts shred on me, both very new. I replaced them in the last several months with good quality ones.

Quick background:
1. purchased 83 300d in July 2012
2. came with a broken/not attached alternator bolt
3. alternator stopped charging
4. replaced alternator with a used one (single pulley) from an 83 240D
5. SSSSQQQQUUUUEEEEEEEEAAAAALLLLLLL!!!!! Lots and lots of squeeling, then burnt rubber smell, then belt failure
6. I spent about 40-50 man hours swapping/adjusting/re-belting/etc. to figure this out and have not been successful.
7. I replaced the alternator bolt and used the mounting bracket from the 240 and finally got the battery to charge as it should (13.8 v running)....
8. I tightened the alternator with all the bracket bolts loose, but it seemed I was tightening it entirely too far...perhaps it wasn't tight enough!
9. but the belt squeal returned and the belt failed. It appears the failure is on the *outside* of the belt rather than the notched inside surface.

PLEASE ADVISE. I'm at my wits end with this thing. My desired result is a charging battery and no squeal from the belt...is that too much to ask, America?!

THANK YOU!!