I purchase the Flex-a-lite 398 Syclone Black 16" S-Blade Reversible Electric Fan, but i don't have it installed yet. I'm still waiting for my variable speed controller to show up. When I did my research, bigger is better. You want to make sure your fan covers a minimum of 70% of the radiator and good rule of thumb is that a fan will require 1 amp per inch in diameter. Also, if your fan is a simple all on\all off design, the initial amps it will pull can be upto double the rule of thumb. My stock alternator is only 50amp max output, so I upgraded my alt. 2 small fans produce more cfm than most large fans. the fan i listed is 2500cfm and from what i read, that might be as low as anyone should go for adequite cooling. I'll be sure to let you all know how mine does once that bloody controller gets here.