[gearhead]

I had a 6.0 with 3.73 rear end. Pulled a Cougar X-Lite 28SGS on flat land pretty good. You can expect sustained high RPM's on long uphill pulls.
Just me, but if you're due an oil change before you go, you might want to throw synthetic oil in it. Shell just released a Rotella T6 synthetic for gas trucks, but about any of them are decent. You may be running some high engine temps up hills then cooling down pretty quick coasting down hill.