Cooling System

I'm looking for some advise/options.
I have a 1971 Duster with a 360 CID and a 904 automatic transmissiom that I use for recreational drag racing only. It has a Mopar viscous fan on it currently, I'm thinking of installing a 16: Flex-a-lite electric fan so I can keep it running to cool the radiator once I get back to the pits. The engine temperature while the engine is running is 190 degrees F. but goes well above 200 degrees F. once I shut the engine off.
What HP advantage might there be by going to an electric fan and how much draw would there be on the battery with the engine shut off?
Any advise would be appreicated.

Thanks Ken Blackman