SCAP also referred to the offices of the occupation, including a staff of several hundred American civil servants as well as military officers. These personnel pretty much wrote the Japan Constitution to which the Diet (parliament) then ratified.
MacArthur was succeeded as SCAP by General Matthew Ridgeway when MacArthur was relived by President Harry Truman for insubordination. With the peace treaty with Japan, the post of SCAP lapsed.