Best possible mileage?

I kept careful notes on my 1969 Dart 225 which I owned 1976 until 1994 (stolen). I got 22 mpg highway, but the speed limit was 55 mph back then. Around 1988 I changed to electronic ignition (Crane Cams XR700), but noticed no difference from the points. The Holley 1920 carb was always finicky, running too lean at idle. Might have done better with larger OD tires.