Daughter needs Gas mileage from 273 commando

I totally agree with the vacuum gauge, driving style is the largest factor when it comes to MPG's My son can take my PT cruiser from 28 mpg down to 16 mpg just by getting behind the wheel. Now for a little old school technology, find an Offenhauser dual port intake manifold for the 273, they are usually pretty cheap(not more than $75) and use a small 5oo cfm carb between that ,the electronic ignition, a 2.94 gear and some lessons with a vacuum gauge that should put you firmly in the 20's
I bought a Shelby Charger new in 1983 with the carbuerated 2.2, at 105 mph steady cruise it would get 42 mpg. At 55 mph it would get 28 mpg. You have to find the sweet spot on the tach and tune the whole car to run at that RPM