Identifying which a/c compressor on a '96 V6

My a/c compressor conked about five years ago.  It now has an after-market compressor and that one is about to conk too.  Mechanic said it's fling freon out the front and wouldn't hold a recharge.  Being that it's a rebuilt, I don't have the OEM part number to go looking for it used.

It's the 3.1L V6, automatic, standard trim.

My favorite used parts shop which I called said there were two models of compressor on the '96.  Does anybody know if that's true, and if so, which other GM compressors would fit (this parts store has a '98 Buick Skylark)?  Or is the store off base?  The guy said something about Model A and I couldn't understand the other one he said on the phone --  it sounded like either Model B, D or T.  Napa didn't say anything about two models when I checked with them if they had the compressor.  And there definitely wasn't a '96 1/2, right?  

The used shop said the compressor's label number would start with 1135, but again, my rebuilt compressor doesn't have that number.  And an internet search for the numbers on this label yields nothing as I don't know the maker of this compressor.  Does part of  the VIN identify which compressor is on my car, per chance, as in which model of Beretta I have, IF they indeed changed stuff in the middle of 1996?  Thanks a ton in advance, as I'm getting HOT.  =)