Steve,
Years ago I was told by the owner of a 1967 Imperial Crown Coupe with the MDO that there were only 56 of these options manufactured during 1967. Later I heard that there were only 10 made in 1968. Though I take both of these answers with a grain of salt, still find them interesting.
Not too long ago there was a 1968 Imperial convertible for sale on E Bay that had the MDO option, the question, was it made by the factory or added by a previous owner?
Take care,
Bill/Imp, 68's