72-78 Dodge 4wd trucks use a steering box that: is the common GM/Saginaw unit, would swing the pitman arm the correct directions and shouldn't be too hard to find. But it mounts to the outside of the frame (and needs the corresponding mounting bracket) which may cause tire clearance problems. IIRc your current box mounts inboard of the frame correct?

In any case you will need a different steering column to mate to the newer boxm might as well get it from the donor truck.

The OE style power steering wasn't a terrible design, just had problems with poor quality seals (newer modern rubber fixes that) FWIW Ford Nustangs (64-73) and 63-80 Vettes used the external ram and cylinders/rebuild kits and control valves are readily availible for those.

Pics of your curret box and mounting will help