318 Gas mileage?

I'm just curious what kind of gas mileage people are getting, and what I should be getting with my 318.

Std bore, mild cam, aluminum intake, holley 4 bbl (vac 2nds), headers, dual exhaust
727 trans
7 1/4 with 2.76s

I've calculated 6-7mpg time and time again.... Should i be getting more?

Any simple tips to improve mileage?