Yes, unique. Although pulley-clutch units are available they tend to be expensive, even from RockAuto (
www.rockauto.com, search for Ford/2002/Mustang 2V 4.6). I bought a compressor
with pulley/clutch for little more from RockAuto. You may be able to source one from a Mustang specialist in the UK. The Mustang GT ones are identical to the ZT260/75V8 the airco compressor already being fitted to the V8 engine units when delivered to MGR by Ford originally I think. Starter motors and sumps are a bit different, but that's another matter!