Vehicles over 13'1" are not permitted through the tunnel in Zion NP. If you are over 11'4" you have to purchase a special permit and can only go through the tunnel at certain times when they shut down traffic so you can have the middle.
https://www.nps.gov/zion/planyourvis...mel-tunnel.htm
I would keep the Montana outside the park. We were there a year or so ago, traffic was a nightmare; glad we were not towing.
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Scott & Alta
2017 Montana 3160RL, Legacy, Onan 5.5Kw, Solar
2022 F-450 Lariat Ultimate