Yeah I agree dodgeman the little A-series water pump has small fans on it which would produce hardly any load. An electric water pump would pull a reasonable amount of load form the battery and in turn an alternator and the effect of hp gain would be negated. I wouldnt want to run an electric pump for the simple reason is that I wouldnt know if it had failed. With the belt driven one I know that if the charge light is on I have probably thrown a belt and hence the water pump is rendered inactive.
An electric pump would be a whole lot of work for little gain.
I still run the factory fan even at 8500rpm!!!.
I dont know how much gain I'd get running a thermo fan as far as HP....but this I know...I was running it all day at wakefield raceway at those revs on a 35 degree day and the water temp didnt get over 80 degrees. I do however have a TF Gemini radiator and a large oil cooler as well from Permacool. it is rated for engines max 250HP ...a little large maybe but the oil temp never got above 60 degrees.