Just n FYI when you arrive at Glacier NP... DON'T try going in through the East entrance with your trailer. There are restrictions on height and length due to the many rock overhangs on GTTS Road headed West. You will have to route south to go under the park's southern border to the West entrance, from which you can access park campgrounds.
I towed a small motorcycle trailer (8 X 10 X 5), and arrived early enough that there was no one at the ranger station when I arrived (7 am), but later, setting up camp, a ranger drove by, asked which entrance I came in, and was shocked they let me through... of course, there was no "they" there, and I simply took a few extra wide turns, made it through OK...