The ratio's were optional , so you have to
look at each differential whereI mentioned for each one. 108,111,113, models can be used. The only one with the 3:27 is the 4.5 eng 108 280SE.
The reason I mention the brakes is that it easier to change out the complete rear .
If you get one with disc, then you have to
change the axle tubes. They hols the calipers and it then requires re- shimming of thr ring gear. Not easy.
Arthur