I don't know the answer to your question - but I have seen controllers that piggyback onto the factory sensor and read their output instead. Might be the easiest way to go.
You want to make sure the coolant is entering the motor at a specific temp, not exactly exiting it.Thanks everyone for your responses. It confirms that I will need to modify a hose joiner with a sensor bung.
Dubie, I remember seeing the sensors installed in the radiator inlet, i.e. engine outlet. There's pros and cons to either, could you elaborate why the engine inlet temperature should control the fan?