You also might check to be sure that fan clutch bearing is not the culprit.
My 65 had somewhat the same symptom. It was the fan clutsh bearing. While
wiggling the end of the blades, the blade tips moved about half an inch. . A
new fan clutch solved the problem. Even if it is the pump, be sure to check
the clutch also. Might save a fan blade from going through the radiator.
Good luck!!
Gene