I didn't know there is a difference for slant engines. I might have bought the new water pump from rockauto. In my 1965 273 engine, I made the "mistake" of installing a later aluminum water pump. That was to fit the radiator bottom outlet, since radiator was for a later 1970's Dart (all Autozone could get then). Problem was the alum water pump is ~1" thicker, which messed up all the pulley alignments and couldn't use my TRW p.s. pump (no brackets for alum w.p.). I eventually got 'er done, but should have researched more and picked my battles wiser. In many ways, slants pose fewer problems since they changed less than the small-blocks until ~1981, though do have the same issues with engine to transmission interface and transmission to driveshaft changes (between 1965 and 1968, I recall).
