Depending on what you want to haul, here is another option. We actually haul 2 road bikes in here with the front wheels removes and the fork mounted on bike tights. Plenty of room for the wheels, helmets, and other stuff inside. Not cheap, but we have used it for 10 years. It slides out about 30" so you can still open the rear doors.
2008 Ford E-350 Quigley 4x4 V10 - 164,000 miles
RB50, PH Top, Dual AGM Group 27 Deka, 2000 Tripplite Inv., No Propane or Water Systems
Van Weight 8,100 pounds, added one rear leaf spring, BFG AT KO LT265/70R17 E Tire press 50psi.