Gentlemen,
Consider looking at Rich Erenberg's site on ebay. He is member of SAE (society of automotive engineers), published numerous articles in the national Mopar magazines, and a long time Mopar person. He resides in Marlborough New York. He has offerings for several styles of pitman arms....small spline box to A,B,C bodies to just about all combinations, large spline boxes to A,B,C bodies, including pitman arms with fifferent lengths for different steering ratios. Many of the parts he reps are NOS. Just google his name or search on eBay for Mopar parts. I've purchased a few things over the years from him...he will answer any ???? you may have.....
Bob Renton