Rent in Denver, heading to Corvallis Montana
Looking at a 2 week vacation , best routes with motels and back roads but not adventure touring. Wedding planed for mid weekend, with road trip each side.
93 is pretty all the way up and down, except for a somewhat boring stretch in the Flathead Reservation.
12 (west) is a super road; I've heard there's been some construction for the logging trucks.
The route 1 loop off of I-90, to the west of Deer Lodge, is quite pretty.
And if you can - do not miss Glacier National Park!