Kelsey-Hayes and Motor Wheel both made wheels for the OEMs, likely others did as well depending on volume, construction style, etc.
The "Magnum" centers for the Fords & Mopars seem to be the same dimensions, so the same stamping could be used.
That's not the case with "regular steelies", which has been well-documented.
Several times, I've used Ford 14x7 Magnums on Mopars, and nobody appeared to notice.