Are you coming via commercial aircarrier or in your own private? The closest real airport is at Great Falls, its a great facility, but there may be small private landing strips a little closer to the Lewistown area. Its pretty desolate prarie in that area, nothing but buttes bluffs and coulees.
If we get word there is equipment on the property I will go photograph it and save you the trip. Its only 4 hours from here and I've driven farther to get a good slurpee, lol.
Robert