I steer clear of the Interstates as much as possible. I've used US 30, 40 and 50 on several trips through that part of the country mostly east of Colorado. US 40 looks pretty tough through northern Colorado so I haven't done that one yet, but we did US 50 through southern Colorado and it wasn't too bad as far as hill go. I think there were one or two passes through the mountains that got to 6 or 7000 ft. Some nice places to stay in and around Gunnison. Plot the route on Goggle maps and see what you think. I've stopped in Sydney and the Cabella's is okay. Lots to see in KS, NE, and Iowa.