John - Yes fronts and rears are different depending on different applications as mentioned. And because of this engineering (number on the part) numbers and paint marks differ also.
Then add to the differences between the two suppliers and in turn which plants they each supplied (typically MADE IN CANADA = Dearborn and NJ MADE IN USA = SJ cars)
Typically the MPC will not list all of the assembly line applications but rather Ford would combine applications so that they didn't have to make, store and inventory all the different ones - only a few. Often the Ready Reference catalogs for each year will include shocks since they were seen and quick moving service items such as ignition, battery and other items.
SO ffrom this point we would need to know more about your 70 to offer more help. Engine, body style, interior package, model, transmission... If you have the buildsheet you would at least have the color markings that would possibly allow reverse look up or cross reference