hi-i have a 66 289 convertible-i had overheating problems in the summer but the problem was eliminated after i changed to a bigger core radiator-installed a fan shroud and installed a 6 bladed fan-

 

I have a 65 with the small shroud and the 5 blade. The only time I ran into trouble with the car was in Phoenix when it was 110+. I never ran into problem in Georgia with it. I am in Warner Robins now, but my mustang is in storage in Oklahoma.