In my opinion, unless you are striving for 100 point concours originality, you should use this as an opportunity to swap the York for a Sanden rotary compressor. The rotaries are lighter, quieter, and more efficient. Plus you can buy them new - someone's used York may be no better than your existing compressor.
The parts needed for this conversion have been discussed here on e9coupe.com. You'll need a bracket from a later BMW.