'66 B-body was plastic; '67 changed to glass with different top bow as previously mentioned. My 1964 Polara 500 convertible had a plastic rear window in the top. Also, as previously stated, the front of the top boot is inserted in a track on the rear seat back. This is a real PITA to remove, so I always left it installed. When the top was up, I would just carefully fold the boot down into the well. I would only put the top up or down after letting the car to sit in the sun and warm the fabric up. NEVER do it cold! When putting the top down, take the boot out of the top well and drape it ahead on the rear seat. When the top is half way down (front portion of top sticking straight up), go back and work out any creases in the plastic rear window by hand so that it is a gentle roll, and lower the top the rest of the way down. Now carefully snap the boot down over the folded top.