Pitman Arm interchange

71 dart with 318, PS and AC. removed worn out pitman arm and replacement (Moog 7074) will NOT work as its splined hole is 1/8" too small to fit on steering box shaft. I know Ma mopar had 2 different sized sector shafts and I may be in that mixip. Any one out there have a solution or Part #? I don't want to have to purvhase all new (73 and up) parts.
71 Dart Swinger in NC