We are making plans for a trip out west this summer (from SC through Yellowstone to Seattle. Found this great article providing information about some of the roads you are talking about: http://www.rvtechmag.com/travel/4_yellowstonebyrv.php?pg=all
Also, I checked on You Tube and you can actually call up videos of folks driving both routes 14 and 16 "from the driver's seat." The article plus the videos convinced us to take Route 16 and stay far, far away from 14. We have a 38-foot diesel pusher with the jake brake, etc. but when I read a comment about Route 14 that said something like...if your MH doesn't have a hinge in the middle!
Good luck with your trip -- we are so looking forward to seeing all that beautiful scenery.
B. Odom