75/76 Dodge Dart /6 average MPG and improvements

The best thing you can do for /6 mpg is Tune it. 73 up has electronic ignition, adjust the gap, get new cap, rotor and spiro core silicone wires. Check to make sure the vacuum advance is working. Get a set of platinum tip plugs while you are at it. Make sure the carb is up to snuff, rebuild if not and make sure your choke is open at operating temperature. As you can afford it, run 2.25 in exhaust with a free flow muffler. That is the best place to start.