2003 2-Dr Blazer ZR2 4WD Auto

My A/C actually works perfectly fine, the compressor clutch just makes a godawful racket, so I set out to do a DIY clutch replacement. The compressor is a GPD 6512124. I ordered what was supposed to be the "guaranteed fit" for the vehicle (GPD 4321259) but it doesn't look like the existing clutch assembly and the inner diameter of the pulley bearing is considerably larger. Is this the right part? I can't see how it could be. And if not, does anyone know the right part number? I'd rather not have to buy an entirely new compressor and have to have it evacuated and recharged, not to mention having to install a new drier.

 

Not really following how the clutch could make a godawful noise; it is either engaged or not. If the noise is coming from the compressor when the clutch is engaged, sounds more like the bearing.