ive had my impala now 5 years ,every year I put a new cardboard package tray at the rear window ,,they warp there is no leak or water in contact with it,last year I put speakers back there to try to stop it no luck.does anybody know of a plastic one or what I can use the interior is black
John Congratulations on your 100th post! It is good to see an active member on the board.
The original package tray was made of Masonite not cardboard. Masonite was an early synthetic hard wood made of waste paper and glue under pressure in a steam cooker. Masonite will resist moisture and is used to construct doors and siding for homes.
You can buy a piece at your local big box hardware store and cut it to fit with a jig saw.
When I was restoring the interior in my 67 I was tempted to masonite, but on 67 there is extra piece that tucks under the window and it's in an angle. I ended up gluing black vinyl on my package tray, looks great.