I think you guys are going way overboard. a mild 318 (318 9:1, magnum heads, LD4B intake, small sumitt cam, 1.5 or 1.6 roller rockers, headers, Electronic ingnition, 600 carter), w/ a 4 speed O/D trans in a A-body w/ 3.23's should net easy 22 mpg...if you keep your foot out of it.