I have researched the different fan controllers for my project, and I think the one made by Spal is the best one available right now.
http://www.spalusa.com/fans/automated/accessories/fanpwm.html

I also think that they make the best electric fans, and will use one or two of them too

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-