Any of the pumps fit any of the engines. The type of pump fitted was dependant on the factory the car was built at more than anything.
They are slightly different sizes but that does not matter. The difference between them from your point of view is the brackets and pulleys to mount them.
Auto Zone still carries the Saginaw pumps re-manufactured originals and Bouchillion Performance sells the brackets and pulleys new re-pops that are exact duplicates as O.E.M.