Every time I change pitman arms it throws the alignment of the steering wheel off. It seems they broach the splines by hand, since every one I get is off a couple degrees from the prior one. Of course, those were all cheap O'Reilly "lifetime warranty" parts, which is why I went through so many. Finally ponied up for a new GM part and haven't eaten one in 5+ years.
I have found the quality of alignment makes all the difference in the world on these trucks. Set it all to whatever specs the alignment machine says is "right" and it drives like ass. Finally found a shop an hour from my home town that does the alignment to his own specs, and it drives like a dream. He tells me every time what he does different than OE recommendations, but I forget what it is, because I now only get an alignment when I get new tires or break a steering box, so every 3-4 years. Hmm, about due for another steering box I think...
The point of that story is ask around and find a
quality alignment shop, and let them check it out / set the alignment. And quality doesn't always mean a big shop. The one I go to is a one-man operation.