OK. That's good.
Atlas apparently used the fiber washers on the 6" and on the mills throughout the production lives of both, because they do appear in all of the manuals that we have copies of from 1942 to 1976.. I would temporarily install the back gear assembly (large gear and small gear/tube), shaft and two eccentrics, and measure the end float. Then put it together with enough of the fiber washers to reduce the end float as low as possible without binding.