Follow the Columbia upstream into Idaho. Lots of backcountry there, so if you have some time, roam a bit. If pressed for time, either hit N. Idaho, Cavanaugh Bay or Moose Creek overnight, then into Montana via the Clark Fork, then visit Schafer Meadows or Meadow Creek overnight, then south either side of the Divide, through Eastern side in Wyoming to CO.
Or, duck south in ID through the Frank Church, overnight Johnson Creek or ???
Then Salmon, through SW Montana, Bozeman Pass to eastern WY.
Lots of opportunities for side trips along either route and good gas stops along both.
Way too many options to discuss here. Pick up Galen Hanselman’s books on Idaho and Montana.
MTV