Is it's JUST for drag racing you just need something to keep the coolant circulating and to prevent overheating due to heat soak afterwards, as even at full chat for a few seconds you won't put enough heat into the coolant to boil it. You will get some localised boiling in the head, but this isn't intended for massive durability so that shouldn't matter.
One or two of the bigger Davies Craig pumps might do the trick as they have simple a 12V controls. There's another supplier that does bigger pumps but the name eludes me. Pierburg do proper OEM 12VDC pumps in 200W and 400W flavours, as used by BMW and Volvo but they are (as far as I know) designed to be controlled by CAN bus. I don't know if you can just wire them up to a supply and run them at 100% duty.
You may want to put a large cooling fan on the rad too to maintain cooling airflow when you stop.