You are in luck, I have a 1991 300D 2.5 and it is a great car. The motor is the 602.962 moyor. Here is a website that may help you.
I also know that Johnson Chan on this website has one with about 290,000 miles on it. I had mine for sale a few weeks ago, but when a guy came to purchase it, I realized just how much I love the car.