440 Dart cooling fan & shroud

Thanks guys.
I have a thermal switch to turn them on/off, and it has a dial to set the on temp. I don't know what you mean when you say upgrade the wiring though. I can run the fans through a relay no problem.
Having said all that, what electric fan set ups would you recommend? I looked on eBay and found 2 that looked good, one was a single with shroud and one was a dual with shroud, and the dimensions were PERFECT but the OE application for both was V6 modern cars. I don't know if these will be enough to cool my car.
Help! LOL

George