Could the diferent diameter wp pullies be because the aircon belt foules on the larger pully. This is a problem Ive had moor than once. Also I once did an engine swap where the car had power steer and the wp pully had to be changed because because you couldnt fit the ps belt between the wp pully and the harmonic.I dont know much about part numbers because books cant doo up nuts.
Cheers Nath.