I contacted MB Grangemouth when i needed a front set for my CLS , they took the VIN and ordered the correct ones. When they arrived at the dealers i took the struts through an they fitted the new springs while i waited.
Some MB's have more than 3 listed because of all the variants available , as said , do your best to try find the colour markings painted on the springs currently fitted to the car (assuming they have not been wrongly replaced by a previous owner) it can really be a bit of a minefield . I discovered this when I replaced all springs shocks and struts on my 2006 C55 AMG .
Just to add to it the rubber part between the spring and the body comes in 5 (from memory) different thicknesses , something else you need to get correct .
Don't forget the stainless steel shim at the bottom of the spring either. Bit like this. The amount of burls moulded into the rubber part indicate its thickness (so adjusting the ride height of the car) , the original P/N is in such a position that it can be seen from under the car and so can the burls.