From West Yellowstone go south through the south entrance of Yellowstone Park (start out early morning to avoid any critter jams). Stop at Colter Bay. That's 87 miles.
From Colter Bay continue south on 89 to Jackson and on to Alpine. Pick up Hwy 26 at Alpine which will take you to Idaho Falls. Pick up I-15 to Pocatello and I-86 to Burley for a total of 271 miles from Colter Bay.
If you take the steep pass from Wilson to Victor on Hwy 22 and pick up Hwy 26 as above, you will have driven 253 miles, saving only 18 miles!
Hwy 26 from Alpine is the better driving route with an RV.
Full-Timed for 16 Years
.... Back in S&B Again
Traveled 8 yr in a 40' 2004 Newmar Dutch Star Motorhome
& 8 yr in a 33' Travel Supreme 5th Wheel