Diesel pusher overheating

I have a 2003 Safari 36' rear radiator with a CAT 330 HP engine. I am the original owner and the coach now has 42,000 miles on it. We live in No. Nevada where everything is either up or down long grades from 4,400' to 8,200'. I tow a 4,500 vehicle 100% of the time and my engine has never exceeded 190 degrees, never. Whenever I stop I get my infra-red thermo out and check the radiator, CAC and tranny cooler, they are absolutely consistent! I never downshift on grades as CAT factory techs have told me to lay into the pedal and let the engine and tranny talk to each other. They know what is needed. I travel north from Bishop, CA to Conway Pass (5,000' to 8,200')frequently and do the speed limit all the way (55MPH)& have never had to downshift nor has the engine heated up. In my experience I just don't buy the rear radiator nonsense not being able to handle the heat. Just did this same run 2 weeks ago at 2:00PM and the outside temp was 101. On the last run up to Conway Pass my rig was just about maxed out GVCW.