http://helenair.com/news/local/biologists-seeing-more-grizzly-bears-north-and-south-of-helena/article_109181da-53ab-5ddf-bb4f-d135fb3d0c4f.html
It's a good idea to carry bear spray in the Rockies, but the stuff is expensive, $50 a can.
Also, while Mullan Pass road is still passable with a two-wheel drive vehicle, the road above Skyline Trestle has deteriorated greatly, with deep ruts, but worse are the sharp rocks. Any speed above 5-10 mph risks tire damage.