Originally Posted by Janet's Husband
The rock guards are just Acrylic Sheet. You can purchase it from plastic distributors and most glass shops. You can get it in various tint densities to meet your needs. You will have to drill out the corner rivets in order to disassemble the frame, but it is easily done.
Gary, I believe you are thinking of the rectangular rockguards. The rock guard for a '71 would be curved and contoured. The original frames were very flimsy and the thin plastic was moulded in a bubble shape to clear the underlying support arms (see attached image). I have the frame from a '71 Caravel
hanging in my toolshed just in case someone ever comes up with an easy and viable method of replacing the pane.
There are several other threads on this same topic and I do not believe anyone has had success in putting a new Lexan or other pane in the old frame. The frames on the newer rockguards are much sturdier and have a rubber gasket around the edge which seals against the body when closed.