I love US 14A, but I have a light fifth wheel and a diesel truck with an exhaust brake. It is a fantastic drive through great scenery, but, as many others have said, better left to experienced mountain RV drivers.
I also would not go through the East Entrance to Yellowstone without stopping and spending at least a full day at the Buffalo Bill Heritage Center in Cody. It is probably the best Western (as in "The Old West") history, art, culture, and natural history museum complex in the world! If you haven't been there before, don't pass it up. I have been there multiple times and see something new each time. Trust me, it will be one of the highlights of your trip no matter how much time you think you have for a "side trip" on your way to Yellowstone or how much you "hate museums."
