WRITE UP DONE BY "lrazer"
The fans I used for this install come out of a 95-97 Ford Windstar, These fans pull plenty of air and the shroud matches up pretty well with the GM radiator. It is the same width and is only about an inch shorter top to bottom.
First of all you need to remove the stock mechanical fan and fan shroud. Next mount the Windstar fans on the radiator, some trimming is needed to fit around the hoses.
Once you have the Fans mounted how you want them its time to wire them up. Here is a diagram that I drew up.
This is the way I wired up my fans. I wanted one to come on automatically with a temperature sensor and the other to be controlled by a switch. You can wire your fans this way or both to toggle switches. You could also wire them both to temperature switches that come on at different temperatures if you wanted to get really fancy.
There are ports you can mount the temperature sensor on the sides of both heads, on the intake manifold, and some water pumps also have a port on top that can be used. However the water pump is seeing coolant right from the radiator so you will need a much lower temp switch if you use this port. Painless Wiring makes temperature sensing switches for fans, Auto Meter also has temperature sensing switches for their warning lights that also can be used. Both these types must be used with a relay.
Here are some additional pictures.