I agree, the Ultra Vans are way cool, and they were way ahead of their time. True monocoque construction, like an aircraft fuselage. The holding and fresh water tanks formed an integral part of the structure. And of course the Corvair power plant. After the Corvair went out of production they made a few powered by a small Chevy V-8 using a marine drive to the input of the Corvair transmission (which was still being used in the Pontiac Tempest with independent rear suspension).
I'd love to find one for sale - they only made about 700 total, but a surprising number are still on the road.
If they're still at the park, any chance you could forward some contact information?