Fit a genuine fan!
I have a long record of being against electric fans (sounds like a broken record, really). I don't believe any of the performance and economy figures claimed by companies like Kenlowe - they measure energy consumption of an engine at high rpm with a fixed fan on a bench, ie with no airflow from vehicle movement. When do you think you'll be doing that with a vehicle? The reality is that at high rpm, with the fan turning fast, the vehicle will usually be moving fast too, so the airflow from the vehicle motion reduced the angle of attack on the fan blades to nil - it'll be windmilling, not driving. At idle, the power consumption from the fan is negligible - the fan is turning relatively slowly and the viscous clutch will be open.
Claims about energy saving are false. The energy to drive a fan still has to come from the fuel tank, whether it's electric or engine driven. But, with an electric fan, the energy has to change state to and from electrical energy and overcome the inherent losses associated with that, plus it has to overcome the friction of the bearings in the alternator and fan motor and the electrical resistance of the wiring, while an engine driven fan has no extra losses being driven by the water pump, which is already turning. Electric fans also run your battery down by being active after shutting the engine off.
The biggest factors are reliability and capacity. Electric fans are not that reliable and are puny by comparison to engine driven fans. Viscous fan clutches normally fail safe - they seize up so the fan will be driven even when it shouldn't, but if they fail open, then a cable tie works as a temporary repair and retains full cooling. An electric fan can only fail in one manner, and it could leave you stranded.
There is a good reason that electric fans are only fitted to transverse engined vehicles or cars with odd shaped engine bays - it's because they're crap. Every car made with an in-line engine has an engine driven fan. If there were any performance or fuel economy benefits to electric fans, that wouldn't be the case.