I'd also recommend 75 to 93. Beautiful drive. Plan to spend at least a couple nights in the Stanley area. Sawtooth Nat'l Recreation has some nice campground and there an many forest service campgrounds along the river.
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