I agree with Dodgeman, but I'd like to add my $0.02... 6 amps will get you a 30-37 gpm pump according to the Summit catalog, for a measly $260. You're probably going to need to upgrade your alternator unless you already have one makes sufficient juice to run headlights, heater, wiper and waterpump at an idle. My guess is that's about 30-35 amps, at an idle. Need to understand here, alternators aren't rated at idle, so take that into account. Dodgeman is correct in that you'd have to run a belt drive on an electric waterpump as there are no pumps marketed specifically for the "A". That means with an electric pump, you'd have two belts instead of one. (you do want to keep the alternator, right?)

My opinion is that at idle, it's going to take more power to run an electric waterpump, and at rpm it will save power at the expense of coolant flow. Then you have the complexity of another belt drive and electric motor with wiring. Seems like it would be a whole lot simpler to run an underdrive pulley on the waterpump. Any competent machinist could make one for a fraction of the cost of an electric pump.