I would definately go a different route once to denver, then going straight west. You'll have to cross at least one ridge no matter what way you go. Monarch is a 6%, curvy, and long, as it tops 11,000 feet. Its not horrible, as Ive done it numerous times loaded in an 18wheeler. If you go down us285 out of denver, youll also hit Kenosha pass, while not very high, its one more to go over. Id suggest I-25 south to C.springs, and take hwy115 by fort carson, and cut off a few miles, vs going to pueblo and grabbing hwy 50 there. Hwy 50 does get to be slow going from gunnison to montrose though, IMO with a trailer. Overdrive will be out of the question even on flat ground out here for your setup. Make sure you have trailer brakes that work properly, and make sure you know how to decend steep grades that go for 5-10 miles. Leaving it in drive and riding the brakes down any of the big passes will result in a nice little fireball. We see a few dozen vehicles in my shop every summer from flat landers smoking their brakes out here, just to warn you. Other then that, have a blast out here, and spend lots of your money with us,lol.