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It would be best if you posted your year, make and model with questions such as this.
For most '60s GM A and B bodied cars bright zinc is the correct plating for an alternator fan and pulley.
My plater gives the best prices when submitting things in batch; an alternator fan and pulley are small potatoes to the usual plating establishment that does jobs by the pallet.
Remember that prep is everything as well; according to my plater the ideal prep for your items would be blasting in 180 grit aluminum oxide. This is a set that I had prepped for plating:
It seems no matter what size batch I bring him it is always around $75, even with multiple finishes.