According to this page
Mercedes Benz EPC 124.290 Chassis Information | Everything Benz
The engine is a M103.985
Automatic transmissions 722.342 or 722.346 (probably not this one as it was Europe issue)
Here the 4Matics are cheaper than the other equivalent models because they are expensive to fix.
All the W124s I've seen rot like any other Mercedes I've seen with rust issues in four main places => behind the front wheels and in front of the rear. I've noticed that cars with rust behind the rear wheels and in front of the front wheels are usually more gone than the others with just rust in the four corners of the floor pan area. (Massive generalisation I know - but we like sweeping statements here)