You would think so, buy my mileage sucks. I've had it around town and also on the freeway for 100 miles or more and it gets maybe 10-12 MPG. As mentioned above, there has been very little work done on the car to keep it up to snuff. I suspect all the PO's just kept it running and drove it. I think the carb (Carter BBD) is just plain tired. All of that should improve with the 4-bbl upgrade.
Well that's no fun. Hard to believe my clunker made it home and your completely rebuilt everything beauty did not.