When we left West Glacier headed for West Yellowstone, we went to 206, south to 83 down to 200, east to 141 to 12 into Helena and picked up 287 into YNP. I verified that all those roads were good for a 40' MH with car. It was a beautiful, scenic drive with no interstates, which is how we like to travel. Enjoy your trip. Betsy.
Betsy