I am trying to find out what the 2 side pieces are called on the convertibles. it looks to cover the area that the cyclinders should go it has three button head screws that hold them in. Looks like plastic tray

 

I call them piston covers, but can also be called rear upper armrest panels, or such.
They should be metal for that year, and are covered with upholstery matching the seats. There are two metal uncovered top covers on them also.