Stock 74 Duster360, 727 and 2.45:1 rear gear with 235/60/14 tires . . . ran 70mph all day long - 22mpg !!

Stock 76 Road Runner, 318 with factory 4spd OD, not sure rear gear, same tire as Duster360, 70mph all day long - 22mpg.

Stock 70 300Hurst (Ragtop), 440, 727, 3.23:1 rear gear, 50 - 80mph (didn't seem to matter the speed), 16mpg all day long . . .

Cheers,