My experience in the mountain West is that as you go up in altitude, boost falls off and EGT goes up. This last week, I was both North and South over I-17 from Flagstaff to Phoenix and back, and climbing out of Camp Verde, I saw over 1300 with exhaust and air filter mods (my personal limit for a long climb is 1350). I was pretty light, with only 2 horses. Also, Southbound, the coolant temp got up to over the 3/4 tick mark, but the outside air was in the 80's, and we were running about 55 in 3rd.
I agree that you need to know what your real weights on the axles are - they always end up more than we think, and as all the states you will travel through in the West have 70+ speed limits, you can overheat a tire in a hurry.