[ChevLoRay]

My son's hot rod '69 had a flex fan, and it didn't overheat. You need a fan shroud, regardless of which fan you run. You also need the thermostat, for the reasons that everyone else has mentioned. They don't cost any more than a couple of gallons of gas, but I understand your delimna. When you have girls to haul around, you need gas, not a thermostat. Gasoline, though, not "gas".

Regardless of which thermostat you use, you may need more radiator than a 2-row core can do for your engine cooling. The heater may help your cooling, when it overheats, but if the weather is HOT and you have girls in the cab, more heat is the lat thing you need.....well, maybe. Let's see....I can always put on more clothes and get warm when I get cold, but I can't take off enough clothes to get cool, when I get hot.....Nah. Don't want to go there.

Your fan blades, fixed or flex, should be about two inches from the radiator, with a shroud, to pull the largest volume of air through the radiator, with the thermostat to restrict the flow of coolant, allowing it enough time to stay in the radiator and cool down.