If you are looking to upgrade to the turbo motor, here is what your are looking for!! I have this motor for sale from a 85' 300D. This motor runs great and has only 145k mile on it. Car was parted out due to rust in the driver side front spring tower. Car was driven up to a few weeks ago. Price is $1095.00 for motor only, starter, alternator and transmission are not included, but are available. Drop this right in your G wagon for more power! the video is of a cold motor and it starts right up and purrs like a kitten! Contact me at vonsmog.com for more info. Have many Mercedes W123 parts.
Video of motor running below.
https://www.youtube.com/watch?v=VOHD2nm8fwU