Former Montanan here..
2 or 3 for small streams--limestones
fun to have not really needed
4 or 5 for putzing around big hole-upper madison
6wt. fast action -summer time and fall fishing mids like the Madison
8wt. for fall fishing big rivers Missouri and yellowstone
with streamers- wade fishing streamer,shooting heads The way to go-some really long shots needed to get to the best holds on bends-
if you go with an 8 get a 10 or 11 hi density head and carefully cut off line from the butt until it balances your rod for those looong casts.
The shorter the head the better and of course helps if you are up against the bank-
in 31 years out there never fished from boat but did use canoe to get to good holds.If your goal is to fish for big fish from mid sept.to march[okay spawners and returners ]on rivers with lakes you will do far better to wade as you will want to go long and deep most of the time.You will see the boat boys going right over where they should be fishing in the fall after the sun comes up.That includes guides-just chuckle..