My '72 is missing an engine-driven cooling fan and clutch, and I scored one from another owner; however, the hub appears to be seized.

Correct me if I'm wrong, but at ambient temperature, I should be able to turn the water pump pulley mounting flange by hand, yes? And there should be molasses-like resistance in the clutch itself?

Correct. You should be able to turn it by hand and there should be no discernible play or wobble in the shaft bearing.

Thank you sir. I suppose I could use it, but I don't really fancy my Z sounding like a Mack truck all the time...

Will order a new fan clutch.