Gary - here's the diagram of your pump in the 1964 edition of the Chassis Catalog for 1956 and earlier models. The diagram doesn't give the part number of the complete pump, but in the text section it lists the pump for 55/56 big truck models with the HD 239/256/272 using B6T 8501-B. Parts Voice says Green Sales in Cincinnati has one. Maybe they'd send you a picture of it.
This book lists the B6C 8501-B I cited on your other thread as used on non-HD 272s. Stu