I have a different alternative for you. Instead of starting in Eugene Oregon, start just north of Seattle Wa. on the northern tier which takes you directly to Glacier National park, from there it's a short distance south to Missoula and your back on the Transam. The distance is shorter, you get to see the Northern Cascades and you have more time to hike in Glacier. I did the route on my cross country, except in the opposite direction.