Deltarider - thanks for the links. Makes sense. I used the expensive vaccum grease to lube the boss and the inside of the carrier. Figured it was would not run away like most other greases. Once I used this, the little side to side play in the carrier ceased and when I put the carrier over the boss, it creates suction because of the grease. So I am hoping that is an indication that the parts are not too worn out in there.
I also ordered the #21 O-ring. Some say it just keeps brake dust out of the drive side of the hub. However, my flange is a little worn where that O-ring should be. I imagine the o-ring also provides some (probably very little) stabilization to the drive flange.
Lastly, from Dave's comments, looks like I need new rubbers. I am going to use the serpentine method (I may buy similar rubber in sheets and cut out a shape to match the dimensions of the big rubbers exactly) for now given the bike needs to go back together so I can ride it to winter storage. Since I have already spent gobs on building the remainder of the bike, I will probably just buy new cushes and install over the winter.
If it continues to experience side to side play after all the new parts, I know a good machinist who will be able to come up with a solution. However, I imagine it will not be cheap!