Ed, Darwin and Tom, Again thank you very much for your helpful insights. Unfortunately the seller seems to be still looking for the engine code, so I do not have any new information on this particular point. In this connection I really do not know how hard or easy it is to find it. Anyway. Because I am not a real car enthusiast but rather an enthusiast of beautiful things I do not know what the main differences between a 401 engine and 425 engine might be. Maybe it is like always: the higher the number, the better. Can anyone explain it to me in very simple words, please? I already read the article "Evolution of the Riviera - Year 1966" at http://rivowners.org/features/evolution/evpt66.html but now I am a little bit confused because - if I understood correctly – it is said that the only engine offered was the (Wildcat 465) 425ci, 340 hp, code "MW", with a single 4 bbl Quadra-jet carburetor. And until March '66 there was a special dealer option that allowed you to order the same engine with dual 4bbl carburetor which means you had 360 hp instead of 340 hp in the end, right? But a couple of posts above Ed wrote that some 66's Rivieras may have a 401 engine what would mean – according to what is said in the previous paragraph – that this is not the original factory installed engine, wouldn't it? And last but not least, for my better understanding of how different engines could optically look like, do you think that this could be a 425 SuperWildcat with dual 4bbl? an auction on ebay b rgds STEFF