Mileage Question

First things first, if you haven't already give it a tune-up with new plugs, wires, cap, and rotor, check that the carb is working well (no leaks, smooth linkage), check the ignition timing advance, and finally set the valve lash. After you know it's running its best you can try getting a more open exhaust system and a Super Six 2-barrel setup to improve breathing a bit. I'm sure other members can give additional advice...