Bartamos - apologies, I should have mentioned in the prior post that the column is in fact well secured at the frame, floor and dash. The slight upward movement is visible at the top of the shaft if someone slowly advances the pitman arm, so I do think it's within the column.
I will check the bearings this weekend to see if they are seated.
I'm glad you raised the issue of "the assembly up top", as I have guessed at how the parts fit together. The factory assembly manual shows a '55 column assembly, which is different than my '58 and not helpful. The '58 shop manual doesn't have a picture of this area and I have searched the net for any blow-up of how it came from the factory. I took lots of pics when I disassembled the truck but unfortunately not up close enough to this assembly. It seems pretty intuitive and unlikely to be causing my issue, but maybe not?
