Need correct Pitman arm

Hello, I have a 73 plymouth scamp. I am converting from power to manual steering. What is the correct pitman arm that I need? I believe the manual box I put in is from a 72 Duster. It is big spline on the box and I used an adapter to mount to steering shaft. Can I use the pitman arm that was on my piwer steering box? The manual box still has the pitman arm on it but it will not work(has pitman where the nut would be on top of center link) The pitman arm I need would have the nut on the bottom. Moog part # would be appreciated