Daughter needs Gas mileage from 273 commando

Your problem will be 89 octane gas and 10.5 pistons, 2 valve notches and a dome. You will be lucky if it will run on 93 octane. The cam is fine. If you adjust it 5,000 miles after you start it up they should go another 100,000 miles or more without any adjustment. You should get 20+ MPG on the highway. A Vacuum gage and teaching her to keep a steady pedal is the key to MPG. I assume you can tune that carb and distributor. Barracuda's, Aerodynamics, and 273's, efficiency, used to be mileage champs. And for Toolmanmike, The OD trans is sweet for mileage. You want to end up with a 2.76 or lower total ratio. Used to run mid 20's MPG with the Commando 273 and 833 OD. I put OD guts in a small bearing main case so I would not have to change anything else but the shifter rods and tabs. Hoping to be in Greenwood, SC. this year.