I used the Derale adjustable ran controller on my dual electric setup. The part number is DER-16749 and I bought it at Late Model Restoration, but you may be able to find it at a better price somewhere else. It comes with a temp sensor that I ended up putting in the heater supply hose. Google it, I have had really good luck with it so far.
Sounds good. PWM is kinda finicky so you want to keep the load-side wiring on the shorter side (otherwise I'd have mounted my controller inside the car if I could have).