There are tricks to getting great milage. They work even on new cars. You need a combination that is matched to the driving you do. You nee good tires, inflated to max pressure. You need a good front end and alignment. You need to know how to drive for milage. (I dont mean hypermiling..) If it's tuned perfectly, and matched correctly, and driven correctly, you will get mad rewards. My Neon averages 34mph on low octane. It's got over 160K, has a ported head, and is a '97. I have custoemrs getting over 17mpg in musclecars driven hard with big motors. For an engine, I would use a Magnum 5.9L like Dave's (DGC). No need to stroke it for an A body. I would run a 3.91 gear, and an A833OD. (Dave, really, think your car, with 3.91s...lol) The engine would be cammed for peak torque (a flat curve) around 2700rpm. A dual plane intake, and any Edelbrock/Carter carb in the 750 range. With careful building, and tuned right, I can't see much of a problem way exceeding EFI V8s and many modern V6s. Running no vacuum advance is the single worst milage killer on a muscle car. You want one in place if at all possible.