The designer of the graduate student houses now standing on the west side of North Park Street is the firm of William Rawn Associates Architects, Inc. of Boston, designer of many houses on Grasse Road for Dartmouth as well as buildings in the South Block.   (Kessel-Duff notes.)   The graduate student houses replace the pair of 1957 faculty apartment buildings by E.H. & M.K. Hunter (Edgar Hayes Hunter, Jr., 1938, and Margaret King Hunter, designers of the Shower Towers).