He said his mechanic told him he couldn't 
  find anything wrong  with either the shoes or wheel 
  cylinders.
  If I don't buy the car I would at least like to 
  give the  owner an idea as to what is wrong.
  Very un -imperial braking  to say the 
  least
    Thanks in advance
   
   
  My wild guess would be a 
  problem with the booster,  I have had a similar problem with a couple of 
  other Chrysler products from the era.  In those cars the brakes had two 
  settings...  Off and "Lets make close friends with the windshield".  
  In both cases a new booster and master cylinder from my friendly local parts 
  store fixed it right up.
   
                         
  Steve B.