On my data card for my 230SL, built end of Sept. 1966, it lists serialized numbers for the engine, transmission, steering box, front axles, and differential. You can compare these to the stampings on the car. I'm not sure if this data card info was included on later data cards as they changed format over the years.
Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both tops
1994 E420