I researched replacing the overdrive five speed in my '88 190E 2.6 with the direct drive five speed and limited slip diff from a 16V. (I specifically wanted the 3.07 ratio from a gray market 16V.)

It all appeared to be bolt in, but you will need the driveshaft from the 16V too as the direct drive five speed is shorter than the OD five speed or automatic, so it has a longer driveshaft.

Duke