I have a 5 cylinder non turbo in my series III 109. I used the non turbo because I had a 300TD that I drove for decades and I kept the engine after the body rusted out.
The conversion is not as easy as it looks. There are about 50 modifications that must be made for it to fuction properly. First and foremost problem you will have is the shape of the sump. In the non turbo it is not as big an issue. I had the mushroom sides of the sump cut off and an aluminum version of an american v8 style sump fabricated out of the old sump to clear the front diff.
The turbo version has a direct oil line to the sump that will require more fussing in order to solve this issue with obvious ramifications to the life of the turbo if the line is not set up properly.
I am not trying to be negative just realistic. I would love to see a mercedes turbo conversion, I just don't want to be the first guy to do it. I think I was the second guy to do the non turbo conversion.
PM me with your questions.
72 Series III 109 SW Diesel, 03 RR, 98 Porsche 986, 01 Porsche 986 3.6 L