I had the same problem as all of you. It was suggested that i get all the brackets, pulleys, pumps etc from one truck.
Seeing I had everything powder coated I wasn't just going to give up for a simple pulley. I spent countless hours on the internet searching and I found this guy. He actually knew how to measure things unlike all the others I've talked to.
Here's his reply to an email I sent to him.... "all chevy keyed pulleys are either 5 3/4 [#325] to 5 15/16 od. setting the pulley on the nut surface and measuring to the cl of the v--#325-1 1/2"[$15.00] #457-15/16 [$35.00] #509-1 1/8 [$30.00] AND #537-5/8 [$35.00]. THESE ARE ALL EARLY SM. AND BB. PULLEYS AND I HAVE HAVE THEM ALL IN STOCK. the reason i measured from the front of the nut surface to the cl of the v is it`s the most accurate way. all 4 pulleys had 2/3 diff. manufactures and were not held to the height of the outside lip which varried from 1 mam. to the other. hope this helps. "
Here's his email.
bigblockjim454@cox.net