When I replaced my "92 Ford 3/4 ton van conversion with a "98 Dodge Durango 4 x 4, I was surprised to find out that the new vehicle tows much better than the larger one it replaced. The Durango has the 5.9L 360 cu. in V-8, full tow package (lower rear end ratio, shocks, brakes, wiring harness, electric brake controller ((which is unused)), etc), + limited slip rear end, and has been equipped with 10.5 x 31 radial truck tires, which seem to make a big difference in tracking.
The old van produced about 11-14 mpg alone, and about 10-12 towing, and the new one about 14-18 alone, and about 15-17 towing except in the steep mountains where it drops down to as low as 10-12 or so.
The only thing I miss about the older, full sized van is all the room for tools, storage, sleeping, and the dog! Had to build a ramp to get her 175 lbs. up into the SUV! Also, it's much easier to back the boat (when it's home from the marina) down the 125 foot driveway into the RV Barn with the visibility of the new vehicle.