I don't believe any Sunline had that tall of ceilings throughout. The longer fifth wheels had more ceiling height in the back, but the bedroom was short.
With something as small as that, no one could stand up in the bedroom, but I don't believe the height in the main part is much over 6'2" or so.
For what it's worth, it would be difficult to find any RV with that tall of ceilings. I seem to recall the Alfa See-Ya motorhomes (also no longer in business) were known for having really tall ceilings. But that was rare.
If this doesn't work out, if you need to find something small and can't go to a large fifth wheel, look for a small toy hauler. There's some out there like 19' or so, and as long as you have a rear overhead bed, you will have a fairly tall ceiling.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR