If you want to go with a mechanical fan, you can make room for it and place it in the center of the radiator with an early style water pump relocation/adapter plate (search pre-'68 Dave water pump adapter plate), and a pre-'55.1 water pump (it sits higher than the '57)
I have never been a big fan of electric-only cooling fan setups. I can tell when my fan belt flies off, but I can't tell the difference between if the electric fan shuts off because it isn't hot enough, or if it shut off because of a defective sensor/fan motor, and meanwhile the engine is overheating.
Carl
