[Spridgets] Single V belt fan pulley - regular size

[Weslake1330 at aol.com]

Hi List,
 
At the Sprite Jubillee I saw several cars that were running a single V belt  
on a pulley clearly designed for two.  I guess an air/smog pump had been  
removed.
 
My question then is why haven't these owners, one car which was  particularly 
clean and tidy under the bonnett, fitted a single groove V belt  pulley?  Are 
they are hard to get in the USA?  I have a couple if not  3 regular size ones 
I don't plan to use as I prefer the large size pulley.   Are they worth my 
putting them on e-bay USA?
 
Thanks
 
W E S L A K E 1330