Intermountain has a P-S 5277 boxcar in both HO and N that's good for at least as far back as 1974 for some roads. Not too sure about 1972 though. Maybe not.
The P-S 5077 is almost the same but 6 inches shorter (plate B car vs. plate C), so the Intermountain could stand in for that if you're not picky, but again, not sure when production started on that.
Late 1960s cars were all still inside-post (smoothside). Exterior-post (ribbed) designs were mid-1970s+
The P-S 5344 by FVM, Athearn or Exactrail (depending on your scale and preference) really cannot stand in for anything else because that flat roof with the curved sides is absolutely UNIQUE. Nevermind minor dimensions.