Anyone know what size/pitch nut is needed for the power steering pump pulley? I would like to stop by the hardware store on my way home from work.

It has 9/16-18 threads.

Thanks Jim. Any ideads where to find one? I stoppped by Napa, Pep Boys, Kragen and Home Depot at lunch with no luck.

I would check CarQuest. You need a good hardware. I know which ones would have it around here. They are getting few and far between. They have a Valley Industrial Products near me. Here's what they have online. The only problem is you have to buy 50. This is a link to a crown-lock like what they had originally.
http://www.valleyindprod.com/shopping/shopping_cart.php

Rick's First Gen Camaro sells them.

Thanks for the help guys. I found one at Carquest.