Daughter needs Gas mileage from 273 commando

Crappy fuel containing Ethanol is the biggest problem with old engines. I was working at a CP dealership in '64, and when brand new, a 273 with TorqueFlite and 3.23 gears would average 20 mpg and get 25 on trips, but not with today's government mandated fuel. My suggestion is to build it stock and teach her how to drive for mileage, and then just grin and bear 17-18 mpg with an occasional dip into the 20s. Without computers and fuel injection, that's the real world.

My current '64 slant six only averages 18 with a high of 22, but a '63 I had when it was only two years old averaged over 20 and fully loaded managed 27 on trips.