Hi I am in the process of rebuilding the bottom end of my E320 CDI sport on a 2007 (OM642.920) I have been using WIS as a guide for the rebuild and its a little vague about identifying which pistons are left and which are right. When I say vague I mean according to WIS there should be markings on the piston faces which are either 4A or 4B which indicate right and left...I have cleaned all my pistons up to near new condition and there is no 4a or 4b marking only a number with a hyphen which is not refered to in WIS anywhere. Now I am worried that I will get this part of the rebuild wrong and wreck my engine!! Is there any other way of making sure I get this right? I see the valve indents on the piston face are offset differently on the top and bottom (Exhaust valves and intake valves) and looking at my photo reference the valve indents with the widest gap faces towards the center of the block.. Also if anyone has any pictures which show this engine with the cylinder heads off or maybe a pic of the bear crankshaft and conrods, this would be a great help to me at this point..