Pre-2002 CLKs had an engine size indicated by the model number; thus the 200K was a 2 litre.
There is no pre-2002 CLK350.
2002-on CLKs had a change of engine through the lower end of the range; the 200K became a 1.8 litre. The only 3 litres in the range are not Kompressors - 280 (Petrol) and 320 CDi (Diesel).
There is no post-2002 CLK230 but there is a 240 (2.6 litre).