Most of the compressors saw across the board corporate use so there were no Mustang only part or numbers. During the 71-73 Mustang model run approximately 7 different service part numbers were used before the 65-72 catalog final issue in May 75. Some compressors may have several ID #'s, but have the same part number because of constant revisions to the compressors. I'll list some of the tag numbers (there are too many to list all) so you can have a better chance of finding the one you need. All have the 2875 number: D1AA-BA, B1A, B2A, D2AA-A1A, A1B, A2A, A2B, D3AH-A1B, A2B, B1A, D3ZH-A1A, A2A, D4AH-A1B, D4ZA-AA, D4ZH-AA. I know that's a lot of numbers, and if you find a compressor that has a different number , let me know and I can see if it crosses to a good an application for your car.
At the start or end of a production year it is possible to see parts with ID #'s from the previous or next model run on your vehicle. My 7/28/71 built 71 Mach 1 has a D2AA-A1A 1972 compressor on it from the factory.
Hope some of this has made a little sense. Lol