From 1973 Chassis Service Manual Plymouth/Chrysler/Imperial:
Water pump Installation (400-440 Engines)
(1) Using a new gasket, install water pump and tighten retaining bolts to 30 foot-pounds. Rotate pump by hand to be sure it turns freely.
This is for the water pump only, not the housing. Chryco Psycho sounds dead on with 20-25 foot lbs.