Question about replacement engine

I have an '03 CLS6. Timing belt broke and valves are bent. I've been looking at engines on ebay and I see 2 variations listed depending on the 6th VIN digit. My VIN is 4. Most of the engines are 5. What is this digit signifying and are they interchangeable?


After looking through several threads it looks like the engine blocks are the same as far as AT/MT. Is that right?