Any fan from an online vendor or auto parts store will work. There are options (push fan, pull fan) which will allow you to choose which mounting method works for you. If you have A/C, replace the fan with one that will pair with the aftermarket thermofan. I'm not using a brand name fan and I figured 2 x 10" push fans were the biggest I could squeeze into my truck (Gen 1). Here's a link to my thread with the fans being mocked up

http://www.mightyram50.net/vbulletin...ll=1#post70328

I got a shop to modify a radiator so the fan sender is mounted in the bottom tank - this will trigger the main cooling fan when it reaches peak operating temperature. Don't hard wire the fan off ignition power or any location before the coolant reaches the radiator, or it'll never get up to operating temperature.