Rack looks to have 5-6 cross bars, that I am assuming the roof box attaches to. No solid floor though. It almost looks like they took a standard roof rack and flipped it upside down. Maybe so they could clear the vend/window in the back of the high top??
New Van: 2000 Ford E350 SMB RB42
Old Van(sold): 1995 Dodge B3500 SMB RB33