Here is a link to the
Zion tunnel. I know people have said they towed thru it. But the link states that rigs over 13'-1" high or having a combined length over 50' are prohibited. May just depend on the person on duty that day. But be prepared for that possibility.
If you look at google maps street view, you can see the signs that state a clearance of 13'-1" center height of the arch and 11'-4" at the edges.