Power Steering problems

My bro just purchased a '71 Dart. He's having issues with his power steering (jerky movement and wandering steering wheel while driving). He decided to replace the old power steering pump with a new one. However, the pulley from his old pump is pressed on, while the new pump from napa is threaded. This is the non-federal pump he's using btw. So, his question is whether or not he can use a later model pump instead, which uses a pressed on pulley. Is there a pump out there that will work with a PS steering box from a '71, i.e. appropriate pressure? My suggestion was to try and find a federal pump, at least that's what I had on my old '71 Duster, and what I currently have on my '68 Dart. Did Mopar have threaded non-federal pumps in '71? Thanks.