My favorite, although not in a truck, is the road (dont have a map in front of me to look) that goes from the U.S. border in Washington to Kelowna, BC. It's absolutely breathtaking in my opinion. No guard rails on the mountains, no run away truck ramps, just pure, almost untouched beauty. There are some really pretty mountains out there.
Also, I really enjoy I-70 from Denver to Grand Junction, and the road that winds through the mountains from Arizona into Utah. I really love it out West. I really love a lot of backroads in Michigan as well.