[FWB]

again the t-stat opening rating is when it opens, it will have no effect on engine operating temp. when the 160 or a 180 t-stat is open they are the same, same flow same everything. that 20 degrees your stat opens early does nothing for a hot day. your geography isn't a pertinent factor on the temp rating of your t-stat. its what the motor should have. based on the info your stating a car in north dakota should have a 300 degree t-stat. if you have hot running issues on a 100 plus degree day more coolant capacity or some anti detonation troubleshooting is in order. are you running too much CR for pump gas?, too much timing?too lean a fuel mixture? all these will play a role on how hot the motor will operate.