Clutch fan options on my 340?

My '72 340 Demon had a clutch fan on it,( not sure if original). It needed replacing and got one from NAPA. The replacment had a longer shaft and now clears the radiator by about 1/2". This is using an origional 7 blade fan. I believe that a clutch fan will draw less power when not engaged,( not sure how much).
Yote