Not sure this will help because mine is an 89 E150 running 235/75R15 tires with about half the tread gone. The measurements were taken with a straight edge laying on the very front and back edges of the penthouse roof.
Front - 80-3/8"
If your rig is to tall you could installing some smaller wheels and tires for shipping purposes. Load the original tires in the van and then swap at your destination.
Read detailed trip reports, see photos and videos on my travel blog, luinil.com.
Visit my Patreon page: patreon.com/LarrieEasterly
Current van: 2002 Ford E350 extended body camper with Colorado Camper Van pop top and Agile Offroad 4WD conversion.