Super Six fuel mileage

i really dont see 30mph being that hard to reach...

i drove my 68 dart to MATS from Phoenix and got 20mpg on the trip there and back...

BUT i have a heavily built motor, .475 lift/246 @ .050 cam,3.91's sure grip, and run 14's...

and i have a 600 HOLLEY DOUBLE PUMPER CARB!