In answer to GeoBoy, we'll be staying in W.Yellowstone for 6 days. Thanks to Park Country on advice about fuel and dangers on route 191, we'll be careful. And bstar 1952, we were thinking of going that exact route because I really wanted to visit Cody but last winter we had a lot of mechanical problems with our 04 Ford F-250, although we had it repaired, we're not comfortable pushing it through the BigHorns, I hope we're making the right decision. In the meantime, hope you have a wonderful trip. Thank you one and all for your kind advice.