If fuel milage is an issue I would think that the oem 2.88 rear would be in order, keep the RPM's low, that's what all the new cars do, but they do have up to 8 speed transmissions and tall rear gears, many new cars are under 2K rpm at 70 plus MPH, remember in the 60's with 28 cent high test gas milage was not an issue, Clyde -- just a note