Thank for the response Evan. You are right about the "blind spline".
I was asking for an internet friend who was concerned about his '58 GMC. He was removing one of those GM 800 power steering box conversions (same bump steer POS that I had on my '57) and going back to stock.
When the front wheels were centered, the pitman arm on the "new" steering box was clocked about 15 degrees from straight down. The concern was that the steering box may have been disassembled and put back together one tooth off. After much worrying we finally came to the conclusion that if it were one tooth off the amount of turn from centered at the front wheels available one way would be way different that the amount of turn the other way. His did not have that problem, so we pronounce it good.