March is still early for a lot of 'scenic' driving. You could take 89N out of Flagstaff to just beyond Panguitch, UT. Then take Hwy 20 to I-15 and go north a short distance to Hwy 21 west to Minersville & Milford, UT and on to Great Basin Nat'l Park area on Hwy 50, Nevada. Just west (about 15 minutes) of Great Basin on Hwy 50 is a wonderful boondocking area 'Sacramento Pass BLM Scenic Pullout on the south side of the highway. RV overnight is welcome and there are great views, tables, shelters, pit toilet. GPS Coord. : N39.12105 W114.30559. At Ely, Nevada take 93 north to I-84 and Hwy 20/126 into Eugene.
We've done this route a few times with our 40' motorhome. Keep a close watch on the weather forecast for this time of year. The only big city you'll have is Boise, ID and it'll be over fast. A good place to stop around Boise if you're ready is Ambassador RV in Caldwell just after getting through Boise.
Have a great trip!
Full-timed for 16 Years
. . . Back in S&B Again
Traveled in a 2004 Newmar Dutch Star 40' Diesel