I know this is old news to a lot of those here, but it might be of interest to some of the less experienced. I wish I had taken pics of the whole job and I'll try to post some pics when my new radiator gets here and I change it all out.
Basically I'm pretty frugal AKA cheap in many areas so I scoured the local Pick N Pull for my fans and I found a nice dual fan set up on a '98 Lincoln V8 Continental, the cost was $39.00.
I had to modify the mounting brackets with a pair of 3/16" X 1" aluminum flat stock that I pop riveted to the shroud and drilled holes in to mount to the original points on the radiator.
The big problem for me was the electrical. All I know for sure is, don't touch bare wires and don't let any smoke escape. I already knew that the passenger car's fans are powered from the PCM and as the Navigator has no provision for operating electric fans, I had to find a way to do this at minimum cost and also a minimum amount of labor and butchery.
After searching the web and all of the various Ford forums I found that a thermostat operated relay assembly was the only way to go. After more searching around I found the ideal, for me, system at Advance Auto Parts for only $36.00, part number 226204 and it is an adjustable unit with all you need for installation. By the way the installation only took about 45 minutes.
I'm not going to tell you all about more horsepower ar better economy as I did this mod just to get rid of the noise making viscous fan and gain more room at the front of the engine for the turbo(s) that may be installed someday.