Maybe.

From the Benz Parts book for your chassis:

Part # 110-350-10-29 ..Thrust Arm/Left

Part # 110-350-11-29..Thrust Arm/Right
There were two different suspensions on chassis of these years/vintage
They are referred to as either Ball Joint/Trailing Arm suspension with open axle shafts or Swing Axle/Kingpin suspension with Enclosed axle shafts and Compensation Spring.
A diff from one will not fit the other and the Suspension Sytems of each are completely different.

One could call a thrust arm a trailing arm, but that terminology would usually indicate to a Benz Tech that one was talking about the open axle/ball joint suspension.
Regardless, a 108 chassis is Enclosed Swing Axle system and the best/ most available axle that will fit to improve your rpm delima is a 3:27 swing axle from a 108 4.5 chassis.
A 107 will not fit as it is not a swing axle system as used in your 108.012 chassis. Several post have included the proper info.

The best way to get a correct responce to your postings is to specify right from the very first posting the Chassis/Model you would like to know about. Asking a differential swap question without any chassis info except a Signiture of 82 300SD is going to get you an answer for an 82 300SD on the readers pure assumption. ....
Had you mentioned Differential Swap Question for 250S in your opening, you would have the answer in short order. You win with a correct, first answer responce and the reader has chassis specifics to use in getting the the correct info back to you.
There is a Sticky on this at the top of the page...very helpful for all.
The best way to get your questions answered!