I also recommend a thermostatically controlled fluid coupler. That way it doesn't draw any horsepower to turn the fan unless the motor heats up at idle. The coupler senses the temp increase off of the radiator and locks up drawing air through the radiator. Advantages include it moves more air than an electric fan can think of moving, weighs less, costs less, and looks original.
I use a Flex-lite 5718 seven blade fan (rated at 4,000 max RPM), and a Flex-lite 5557 Standard Duty Thermostatic controlled fan clutch (because I have a 1985 car; Your's might take a 5537 which fits the earlier model Chevy's). The fluid coupler by the way turns at one third engine rpm when cold 1:1 when hot so watch the maximum RPM when temps are up. If you are going to race it a lot consider a race fan that the blades flatten out as RPM increase such as the Flex-Lite 1380 which is good to 10,000 RPM (just keep in mind a Race Fan isn't intended for the street, just keeping the car for boiling to the ground during a pit stop).