go with two 10inch electric fans side by side and run a toggle switch on the inside of your car this swap is good for two reasons one you will free up crank power two after running the shit out of your car you can leave the fan running two help cool your motor down once you turned it off .remember to put inline fuse when hooking up the fan you can go to autozone to get all parts for cheap
almost all e fans will not flow as much air flow as the stock mech fan. the stock mech fan if taken off you will free maybe a whopping 1hp. i personally would leave the mech fan on to prevent overheating because when you don't flow as much air as stock or more with e fans you have a very great chance of over heating.
your choice but you've been warned and there are hundreds if these threads. if you search.
I have a Flexalite twin 12", and it is not enough.
(FAL & Flexalite are the same fans, the FAL just costs more.......)
They are rated at 2500cfm.
It is getting replaced soon, by a Derale 4000cfm twin.
But Flexalite also makes a high capacity dual that is rated at 4600cfm.
To run these large vans, it is best to use a large relay (70 amps), and a large fuse assembly.
I have already went to the large relay (like a standard universal head light relay), and fuze.
The fuze is from an audio supply store.
And it needs large gauge wire also.
I use an off the shelf electronics temp switch to trigger the relay, and have it attached to fan mounting point on my Koyo.
I used a 165 degree switch, and have the whole circuit wired direct to the battery.
I can sut the car off, and walk away.
As soon as the radiator cools down, it shuts off.
I have run this circuit for years, and never had a problem with the battery.
I use a ford taurus fan, it works okay, but if I abuse the car multiple times, non-stop I get borderline of overheating. Like sixpack said, make sure you have a fuse and relay. I used (like sixpack said) was a fog light relay kit from an autoparts store.