[QUOTE latef Graflex also offered the Graflok back which was standard only on the late versions with the top Rangefinder ][/QUOTE]
the Pacemaker Graphics were introduced in 1947. The Graflok back was introduced in 1951 or 1952. It was immediately made "standard" on 4x5 Pacemaker Graphics then as an option on other models.
You could special order a spring back or Graflex back on a later year camera if you wished and that option may have ended with the introduction of the Graphic rangefinder in 1955.

A grafmatic should just fit but on some backs the springs are a little too short for it to fit easily.