Only 28? You can go higher with some carb mods. Someone on here was talking about making mods to the carburetor that will increase mileage but decrease driveability. Supposedly he hit 90 mpg in an old Dart, but said that it was pretty much undriveable.
Have a Hydrogen Generator that while I was testing almost blew up in my face, but as repeated, is very high maintenance.
Still have factory Holly carburetor, haven't thought much about heavily modifying it. Have to drive this thing 50 miles interstate every day, don't want to get run over. The mileage I am getting is at 70 MPH!
Called Holly and Edelbrock about their Fuel injection conversions, gave them ALL vehicle specs, both told me I would only see 2-3 mpg improvement! For $1000, Told them to keep it. And, at least I can limp home with a carb!
Also have in a box in the garage a 360 ci engine, so engine load would decrease at 1750 rpm.