You will go through the Eisenhower Tunnel at 11,000 feet and over Vail Pass at 10,600 feet. Your truck will be starved for oxygen and lose 1/3 of its horsepower at those elevations. So you will likely not be able to stay at the 65 MPH speed limit going uphill. But neither will a lot of other RVers and truckers, so just do the best you can--it is only 15-20 minutes of a 4-hour drive.
More importantly, how are your brakes and transmission? They will get a harder workout than the engine. But be sure to use your gears and not your brakes on the downhill side or you might be forced to use one of the runaway truck ramps. That would not be any fun with a trailer!