I believe that I can help throw some fuel on the fire here.
I actually do have most every Ford MPC for many eras of Ford production throughout the years. I even learned to read and understand the books over the many years that I was a parts manager for Ford and Lincoln-Mercury dealers.
I just looked up the pump in question in the 1964/1972 Ford truck book and, of course, it is not listed there. From what I have been able to ascertain, the 4008-SA number seems to be a service replacement number but the date code on the pump does not fit that scenario. The M section of the 4008-SA number will only be found on a Carter box and I believe that the M relates to mechanical as compared to electric.
I encourage constructive criticism here as I am always open to learning new things.
-Fred-