Highway 200 and 83
I biked them from Lincoln to Bigfork and the colors of Fall has never seemed prettier to me. You get to see them a lot on that specific road. You are right between two moutain ranges, it is quite impressive.
The towns of Lincoln and Ovando are really pretty; Ovando as a Gilmore Girls feeling to it and I dearly wish to go back eventually. I bypassed the Clearwater turn by a little gravel called Woodworth which led me at Salmon Lake, 10miles from Seeley Lake. Yes it takes you of of the highway, but it is gravel and you go through bear territory, be careful.
The highway shoulder is not impressive. It is a popular biking road and a really enjoyable ride, the cars know you are around, but still, there are a few scary miles right after Lincoln and passed Seeley Lake and again after Swan Lake. It is not a hard ride, though.