Running without a t-stat can cause the engine to overheat as the coolant is passing through the radiator to fast to effectively remove the heat...the t-stat is also a flow restrictor.
Having a 160* t-stat in your truck won't cause it to overheat, that's just the temperature that it opens...once your engine comes up to operating temperature it never goes back down until it's turned off (unless your running in a really cold climate like Alaska).
Mike B
