It has been a while back but I had a custom pully made for my 54 3100 because I have a/c. He was a guy up in years I believe a GM retiree. I will see if I can find the bill of lading.
This what I have found so far.. But classic industries have a big listing for this item. I have yet to look through my files. I don't believe it I found it. It is called Buffalo Enterprises, 360-652-7684. That was back in 2007. It was listed as a 2 groove damper, $200.00 plus $12.00 shipping.25625 Dahl Rd.Arlington Wa. 98223. I googled and it still shows.