I have a very good 83 240D with an engine I rebuilt that almost went to storage in favor of my next project car that was saved by Pep Boys parts--alternator and AC Compressor. Both components were unrepairable, total replacement at Pep Boys was $230, Total replacement elsewheres, $500 to $800.
I was told that the AC compressor ($135)was a good choice by a reputable dealer's head mechanic, very respected, who had put in 5 of them. The alternator was a Bosch, and had the same stampings as the original! ($98)

Well done!