I have always run a regular 18" fan water pump driven,, Now that i have added a vacum pump, the drive manderel is in the way of a fan, I have to switch to electric. SO, i see a lot fo 16" fans in Jegs etc, what is a good cfm rating??? 2000? Yea its a big block, and used to run about 180-ish with a 180 t stat on a hot day so,,.,,,