MDS, VVT, and transmission options?
There are a lot of guys getting 20 MPG or better, ON THE HIGHWAY. If you run fuel injection, keep the car fairly light (It's why we build A-Bodies, right?), and have a decent highway gear, low 20s is fairly easy.
I BELIEVE that Tincup, with a 5.7L and a late model transmission has reported mid 20s on the highway.
The key is to not drive it like you stole it. ;)
Regards,
Joe Dokes