287 goes all the way from Choteau in the north to connecting to 191 just north of West Yellowstone. Yes, my mistake, but it does cross Ennis, but the OP asked about I-15 to (north) to Helena on 287. As far as I can see, there isn't a 297.
In addition, according to my Road Atlas, 287 is a scenic route. I bet you can go to YouTube, enter in "Hwy 287 Montana Scenic Route" and it'll come up with a video.
Ah yes, editing because I just
found this video on 287 from Bozeman to Helena. At least it will show most of the route.
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