I found the first pitman arm I bought, for my 72' b-body, to be slightly loose on the cross-shaft splines after the nut was tightened. The nut and lock washer had bottomed out against the shoulder, the tapered splined hole in the arm was a tad too big. I don't recall the steering linkage was contacting the torsion bar but clearly the pitman arm was too far up the cross-shaft. Sourced another arm from a different vender to solve the problem. I have never found shims installed under the steering gear originally, don't believe that to be the solution.