whats the best engine for both performance and mileage??

Superior engine?! :puke:lol is he kicked off FABO yet? No :spam1: allowed here! haha. As far as the question goes, My good friend has a 73 duster with a mild 318 that get anywhere from 17 to 20 on the freeway depending on how he drives. Stock bottom end (20k miles) with headers, dual flows, rpm manifold, 1406 carb, K&N filter, and an msd ignition. throttle response is pretty good and it doesnt kill him on the freeway either. (there are many better paths for hp and mpg but this is just something to compare to) oh and hes got a 3.23 gear ratio