The Doty pulley is 5.75 diameter. I've run this one for years in my Coronet without any overheating problems. I use a factory water pump pulley and an Edelbrock water pump. I have a 22 inch radiator so it isn't exactly a killer cooling system.

I have the same size pulley on my Duster.

https://www.dotymi.com/mopar-crankshaft-pulleys/42-mopar-and-chevy-crankshaft-race-pulley-1375.html