I've got a couple. 1. US 12 between Lolo Montana and Lewiston Idaho. 100+ miles of curves and gorgeous scenery. 2. US 191 between Jackson, Wyoming and Grants Village in Yellowstone. The Tetons and the Rockefeller Highway are breathtaking. 3. The Going-to-the Sun highway between lake McDonald Lodge and St Mary's Montana is another killer drive for the scenery. (Know the enemy, if you get a ticket in Glacier, Grand Teton, or Yellowstone it's a Federal offense. These roads can also be clogged with RV's and wildlife induced traffic jams, adding to the "experience". There's still a lot of fun to have because once you pass one park ranger on these stretches, your done seeing them.) 4. US 550 between Durango and Silverton Colorado. Make sure your Z can hack the altitude here, and in Wyoming.