pax britanica - I used to fly those SAS MD-80s with all the locals on them around the northern European countries - all I remember is trying to keep my head below the cigarette strata in the cabin - cough - cough !
Any airplane configurator will tell you that the MD80 config will not be built again because of uncontained engine burst issues. Further, it is not an efficient configuration b/c all the systems run the length of the airplane - rather than keeping propulsion, systems and fuel in the same location - the modern twinjet config with engine under & forward of the wing result in a lighter configuration - that is easier to weight & balance - IE OEW center of lift ..
That being said - many many products are in commerce that could not be certified today - for instance a 1969 chevy w/o seat belts - or a lawnmower w/o a blade brake ..