95 GMC K1500 - engine runs cool

I have a 95 GMC k1500 extended cab 4 x 4 with a 350 (5.7 litre) TBI with 190,000. I have owned this truck for many good years and it has always ran cool. I have replaced and checked the thermostat several times but it still runs very cool like 150-160 degrees even on the hottest days, and in the winter it barely gets warm. Is this common and could it be due to the massive mechanical fan and large engine compartment. Is there a way to fix the problem, such as installing an electric controlled fan.