I am curious though what/where people are getting that information. I have the 63-65 parts book that references the ball bearing (67-1240) and also shows a retaining cup (68-0186) as well as the three different options for shims.
I think you are right, I had a look through the parts books for all the years and the shim cup has always been there regardless of whether a ball or roller drive side bearing is fitted.
However I did note that on the timing side the bronze thrust washer is only fitted on engines using the roller drive side bearing.
I think the idea was that when the drive side ball bearing is used the crank is locked into place by the alternator. When the roller bearing is used the crank isn't locked and the needs the bronze thrust washer as well as the shim cup to adjust any end float.
So as you have the ball type drive side bearing then there should be a shim cup with shims to adjust end float, there should be no bronze thrust washer on the timing side.
Suggest you try removing shims and see if that helps, also are you fitting the cam, breather and pinions at the same time? Could be the cam or something else binding.