Back in the 60s, which is around the time this recipe was published, the choice of pork cuts was a lot more limited than it is now.  You could buy roast pork and pork chops and not much else.  So although this recipe calls for shoulder pork shops you could really use any pork cut you wanted.  As it’s pre-metrics you need to convert the 10oz can of soup to 300ml and bake the casserole at 180o.