You are right TenOC, when you leave St Mary's, you will have to head down towards Browning, but you hit 49 about 12 mi. before Browning, and as you said it is very winding, and watch out for rock slides.
The under pass at E. Glacier has a sign for 12'-8", we are lucky to only be at 11-4 with our class C.
I know when we were at Two Medicine in 2015 it was first come first serve, I didn't know they had gone to reservations. We arrived at 7 AM and found a site we liked, and the people were packing up getting ready to leave, so we waited for them to pull out while we were pulling in, then went and checked in.
2007 Forester 2941DS
2014 Ford Focus
Zamboni, Long Haired Mini Dachshund