I have a 65 and 66 T-Bird I run 160 thermostats in them. Radiators have been check for flow and are good. I want to put the best fan for cooling. I currently have 7 blade clutch fans. What is better a non thermal or thermal clutch fan for cooling at idle? hOW DOES THE NON THERMAL One work? Is a flex fan the way to go? Thanks for any input