Keep the belt fan if at all possible.  Dig around bone yards or call
Summit Racing and see what they can get to cover up that fan.  I've
had many Firebirds and Camaros and the only one that never overheated
was the only with a belt fan.

That said, if you swap in one or two electric fans, those aftermarket
ones that mount with tabs that stick through the radiator work well.
You'll probably end up with the biggest fan they make on the engine
side and another smaller fan on the other side.

For wiring, you can either set them up to run all the time or to run
off a thermostat.  Don't hook them up to a switch - it's too easy to
forget to turn it on.

An aftermarket thermostat can mount to the radiator fins and you'll
need a fan relay.  The relay switches the big power for the fan motors
and the ignition + thermostat turn the relay on and off.  I've seen
all these parts and wiring in a single bag at the local auto parts
store.

Count on a couple hundred bucks to set this up and it won't work as
well as your belt fan.  Bolting in the right fan shroud will help keep
your fingers attached and make the belt fan cool the engine even
better than it does now.