Like 9FF posted, I use the 71* thermostat with the 75* radiator fan switch combo.
Depends on where you live. In AZ, spring, summer temps over 100* are normal.
I change the radiator fan switch about every 2-3 years. The contacts burn and I notice the fans come on later or stay on longer-battery drain.
http://forums.rennlist.com/rennforums/9539673-post2.html
NOTE: The 80* thermostat/fan switch combo works the best for emissions testing.
J_AZ