Try
www.partsamerica.com They are the internet arm of Advance Auto Parts. I've had pretty good luck finding replacement parts from them and they do have pitman arms for Cuda's including AAR quick-ratio boxes. It usually the same stuff as Year One, but substantially cheaper. I bought a remanuf. steering box from them for $120 w/ $30 core. At Y1 it was around $300 w/ $75 core and it was the same box, by the same remanuf. (Lares). I'm not knockin' Y1...bought from them before and will again, but money doesn't grow on trees around my place.
If you have an Advance Auto Parts store near you, simply get them to order the part, they'll drop-ship it to that store (overnight in the Atlanta area) and you don't pay any shipping charges.
Hope that helps.