Any Toyota Techs on here?

Fan clutch has nothing to do with it. Thermostat controls temp. What is gauge reading when heater blows cold?

My thoughts too. Fan is certainly a part of it all, and a proper clutch can gain you some fuel mileage and better acceleration. I like direct drives on big blocks. Most of what has happened to this car has actually improved the cooling system. And that is beneficial. I see no reason to try and defeat the system. Just do what I have done for 45 years. It's free. A piece of cardboard. When temps get close to 40 F toss it.