Mechanical fan + pusher fan question

Note that using a lower temperature thermostat does absolutely nothing to cool the engine in high ambient temperature conditions. All it does is open the thermostat earlier. After that it is up to the fan or road speed to keep the temperature under control.

Combustion is more efficient at higher engine temperatures. I always use a 195º thermostat. This keeps the engine temperature constant regardless of the exterior temperature (until it gets into the high 90s, at least), and provides effective cabin heat in the winter (which a 165º thermostat does not).

One problem with a pusher fan is that the fan motor and frame blocks airflow to the radiator, so it pretty much has to run constantly to compensate. It is also inherently much less efficient than a puller (compare the effect of blowing air through a piece of window screen, versus sucking it through). An engine-driven 7-blade clutch fan and a shroud would probably be more effective.