V12 engine differences question
 

Hi All

My 1994 SL600 has had an engine change. The replacement engine is from a 1993 600 SEL.

I have noted that the engine numbers are slightly different and was wondering what the major difference is.

The original engine number was 120 981 xxx while the replacement is a 120 980 xxx.

Is there anything I should know about that is significantly different??