To make things clearer I am looking at a documented 87 420SEL (from Carfax and the title) via the vin #. The current owner claims that he has replaced the original engine with a 560SEL engine (5.6). Im asking if there is a visual way to determine the validity of his claim short of tearing stuff off the engine to find the actual serial # of the engine. Im aware that the 560 air cleaner has two intake hoses and this engine has one. When I pointed that out the owner reminded me that the 420 grill is designed to accomodate 1 hose so he had to use an original 420 air filter config on this 5.6 engine. Unless theres an easy visual reference other than the serial number then Ill make the potential sale conditional on my Merc mechanics inspection and let him solve my dilemma.