Yeah, that's the biggest thing. You really don't want the fan to run all the time. It kind of defeats the purpose of less draw and wears on the alternator. In theory the fan should be off when highway cruising, therefore giving you the best gains on the highway. The easiest way to do this would probably be to get a wiring set similar to OP's. One with a temp sensor that either has an electrode stuffed in between the radiator fins or even better a temp sensor in the coolant flow. They are either preprogrammed to come on at a certain temp (185, 190, 195, etc.) or are adjustable. Most fans like the ones I mentioned above are two speed fans though. There are wiring kits for this, and that would probably be the best way to go.
Just check out the power of this thing:

 

This kit looks the way to go if using a junkyard Mark VIII or Taurus two speed fan. It has many options. I think I'd go with the low speed at 185F option along with the toggle switch for off road or towing situations.

Mark VIII, Taurus, Two Speed fan relay kit.

Here's a good explanation of the kit by its creator

http://www.thehollisterroadcompany.com/MarkVIII.html

 

My apologies for thread jacking BTW! Just thought this was as good a place as any to share ideas about this.

 

No worries...I was just sharing info, not asking questions. The more info the better. Sounds like a cheaper way to get similar resilts as mine.

 

thank you for this thread, every time I seem to come up with an alternative idea i am told to just replace it with stock, even though it sucked when they made it.

the way I see the alternator, it is spinning one way or another. adding a cooling fan to the mix is no big deal. many cars already have them and their alternators are not failing prematurely because of it. I wont get into people and their car stereos.

again thanks,.

 

I talked to the company and they steered me toward rockauto for the fan with lifetime warranty (Dorman 620118) for $67.79 1995 FORD THUNDERBIRD Radiator Fan Assembly
Our radiator core measures ~18.5'' tall by 25.5'' long. This shroud measures ~18.5'' tall by 24'' long. So about a 95% coverage!
Here is a forum thread from high hp V8 kit car drivers who built the exact system and like it a lot.
Cooling Fan Upgrade - FFCars.com : Factory Five Racing Discussion Forum
My only question now is, what temp should the low speed fan come on? I'm thinking 210F, which is high, but it doesn't shut off until it cools to 195F. I would like it to be off while on the interstate, so that seems like the best option. Thoughts?

 

If the new fan is not small enough to fit with the stock upper fan shroud on, you'll have to deal with 2 loose hoses at best, or hood clearance problems at worst.

210F seems high. I'd set it to come on with the factory thermostat.

 

If you run the 180F stat, at freeway speed you should be 180 - 185.

 

Yeah, I know. Guessing maybe a plugged up heater core. The radiator was changed about 6k ago. Needs more investigating.

EDIT: I already am running a 180 tstat. Maybe got a bad one? Like I said, I need to investigate more.

 

Take it off and boil it and make sure. Especially if it is a Motorad! I have had horrible experiences with Motorad not opening much at all if any.