I would just do things a "normal" way. Everything else seems like your asking for trouble. If you buy you vehicle out of state, buy it, bring it back to your state and plate it, pay whatever is necessary, then when you get to montana, hit up a DMV there and tell them exactly what you intend to do and how you should handle it. If it is allowable to "tour" the state for 30 days (assume in various campgrounds) then do so. I would also guess this is your time your spending to find your "home", so once you do then start the paperwork as necessary to plate you vehicles in that state and whatever.
Why mess around with all the LLC stuff unless you a legitimately running a business? If so, then why not contact that states authoritys on the matter and ask them how to proceed?
I must be missing another post somewhere...