where can you find one?according to my book by NITSKE there are no w123 models with that rear end gear.the only model i can think of with that gearing is a w126 body.Wouldnt you need modification to make that work.I am thinking about putting a taller gear in a 240,like a 3.07 from another w123.unless i can find a five speed for around the same price...but i think the former will happen first.I recently got less than 22mpg on a three hundred plus mile round trip.About nintey percent of the milage was on the highway.I was doing between 70-75 on the highway.Still that is only a mile or two more per gallon more than a 12 valve cummins powered ram i used to get 20 on the highway with.i dont mind being a little slower either.if i am not in a hurry i will put on the ipod ,listen to my podcasts(not music,yes really)and watch the gluttons pass me by at like i am standing still at 59mph.all while getting 5-10 mpg more than them and taking only a third or a quarter more time to travel the same distance.