Have you replaced the thermostat yet?
If you do, the OEM Ford one should be fine. No need for a cool one unless you want to seriously track the car.
You can test your current one this way:
I'll have to pop my hood and look, I'm not sure how the fans work. One may be the A/C fan and the other a two speed, or one is low speed and one is high speed. I'm not quite sure, but I'm guessing the first. If it is the first, it sounds like your resistor pack is shot.