As for another option to throw in the ring, when I bike from Crater Lake to Eugene last July, I rode 138 and then picked up "Diamond Drive", a 70 mile route of Forest Service roads that got me to Oakridge, and from there 58 into Eugene (mostly.) Diamond Drive is remote and scenic, but also features 20 miles or so of gravel, some of it a bit rough, but I found it mostly manageable with my LHT with 35 mm wide tires. It won't be everyone's cup o' tea, though.