Towing a vehicle that weighs more than the vehicle doing the towing isn't all that bad. Yes, you can feel it back there, especially on badly rutted highways. Just be sure all towing components (truck's receiver, tow bar, bracket, safety chain etc) is rated for more than the van, and drive appropriately for the load and conditions. A supplementary braking system will be a must for that combination, but be sure to use engine braking to control downhill speeds, to ensure your brakes are still nice and cool for emergency stops.