I'm sensing a fear of rpms here...redline is what, around 3300? My tow tunes like to shift closer to 3000 and the powertrain can handle it. Drive by EGT and Trans temps below the limits and you are good to go. It's a fine towing machine...lol
What he said. Let the transmission do its job. Higher RPM = Lower torque for the same HP. Let it wind out - the governor will keep it from blowing itself up. The real worry in the mountains is not climbing the grades. Its getting down them safely. I've said it many times but its worth repeating - you can go down a grade too slow a million times but you can only go down it too fast once.