Saginaws had at least 2 reservoir designs. The first one here is what some people call the "Canned Ham".
See why? The shape is also sort of like a bowling pin. The second is round with a steel neck. Both use the same pattern at where the pump itself slides into the reservoir.
The other design....
Original slant six pumps put out around 900 psi of pressure. The V8 versions put out about 1100-1200. The pumps were essentially the same, the pressure differential was made up with shims here: