Mpg on a mild 360?

I did about a 1300 mile round trip in my 70 Duster a couple of years ago, and got about 14.5 mpg. That was with a #587 head 360, about 9.5:1 compression, stock 340 cam, cast intake, Edelbrock 600 carb, and 340 exhaust manifolds. Also an A904, and some 2.94 gears specifically for the trip. That's with two 250+ lb guys and a weeks worth of gear onboard. We did a LOT of 80 mph, and looking back, it's more like we were trying for tickets, rather than economy...