I know of which you speak. I had real trouble putting them on my 300SDL and 300D (W123). I also replaced the larger bushings at the base of the shift handle in the 300D so that me taking both ends out and doing them on the bench practical. I found out the special tool sold by that guy on the web work by pushing them in short of crooked. If you get one side in place, then the other side doesn’t have to stress is for her to follow suit.

But I had a devil of a time getting the shift arm back on the tranny on the 300D. The neutral safety switch on that model has a much simpler construction. It mounts onto the lever, a little toggle arm anyway. When I discovered that I had to remove it and do it again. Somehow I survived.

__________________
Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K