In my experience a 360 is a 12-13 mpg motor/ no matter what body its in, in town, on the highway, towing, not towing, cruise control on or not, flat land or hills,

Different animal, but I had a '76 Club Cab that originally had a 360 that I swapped for a (stock) 440 and got better mileage.

While I've never had a Magnum 360, I have had a few of the pre Magnum ones and they all sucked gas.