dual batteries

With an electric pump, sometimes you don't need the fan on and you obviously don't run the engine. If the radiator is large enough, the water flowing from the pump will bring the temp down.
Back in the day, I had a quick release top hose on my Duster and would pour gallons of water backwards through engine to cool it off in staging lanes. Yes, a long time ago!
I used a moroso electric motor and cog belt to spin water pump.