Forgive me if this is a question has been asked a thousand times before. But,I've searched all through these forums and I've found many different answers. I am about to start the rebuild of my 1984 500sl's motor to seal some oil leaks and fix the exhaust smoking issue. I've been told that the motor is not the origional 117.962 and has been replaced by a 117.963. It has the Tri-y exhaust for a 107 motor ,without cats. It has no charcoal canister, no o2 sensors, no #3 port on the diagnostic connector, etc... I have little or no history on the car other than is was mostly a southwestwern car and was purchased in Germany and spent a year there before it came to the USA. So i have no idea why the motor was switched. It sat for 4 years before I bought the car and, I am at the last ( hopefully ) stage of the restore. My question is ... how do I determine which 117.963 motor this is ? I've heard that the 117.963 can be a euro, or a us or an amg ? What should I look for once the motor is open ? Is there something the motor serial # would tell me ? Is there any real difference or am I splitting hairs ? Thanks in advance for any advice..