I ran across a nearly dead-on muffler replacement for 600 coupes. It's 6" round with length of 11.5". It has offset 1 1/2" pipes coming out each end and those bring overall length to 16".
Go to http://www.imcoweb.com and the part number is CM43 (smaller typeset number is 151716). I seem to recall buying several of these through either Summit or Jegs, but can't swear to it.
These could also fit the sedan, but would require moving the input to the side as is on a stock sedan muffler.
Hope this helps someone out, as finding replacement parts is becoming an art.
Richard Morris, owner of at least 2dozen 600's since 1974.
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Replacement mufflers for coupe
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