You'll find a kinds wiring diagrams.
Harnesses have options for single or dual fans. I've run both.
I currently use a Painless wiring harnes. It runs both fans. It has extra thick wiring. It helps since I use a 145 amp alternator.
Here are a few examples:
http://www.fordmuscle.com/archives/2...cfan/index.php
http://www.s-10crewcab.com/%7Ehenryj/fans/fans.html
http://www.s-seriesforum.com/how-to-efan.html