Many years ago, I grabbed 240z steering rack from a salvage car in a yard. My thinking at the time was that I could send it in as a core on rebuild exchange some day. Tonight, I removed the retainer nut and screw, and found two washers - one thin and one thick sitting on top of the spring. There was no shim under the spring - the spring was sitting on the bronze retainer. Since the rack has been in my possession since the 90's and is covered in tons of gunk, I assume it has never been apart.
Of the three youtube videos I can see, one puts the washer(s) under the spring against the bronze bushing, one puts the washer(s) on top of the spring, and one has no washers.
There are no shims in the picture in the factory shop manual which identifies all of the parts to the rack (15, 16, 17):
I suppose it is possible that the shims were used to adjust the amount of spring tension pushing the retainer against the rack... with the retainer screw in the precise installed position per the factory manual instructions. Steps 12-15 pertain to the retainer and retainer screw installation:
Perhaps originally, they were added by factory worker in a fashion such that, the retainer screw was set per factory instructions, and then some type of resistance check was made. Then this was followed by adding shims (remove the retainer screw, add a shim, replace retainer screw, then check resistance again... Anyway, that is my guess.
Another interesting thing I am just now seeing: the retainer spring I took out of my "undisturbed" rack does not match the specs for the 71 manual, which are here:
Free length is about .890" and it is only composed of just under 4 coils.
Odd!