It has been a lot of years now but my '68 originally had a thick insulation top well liner in addition to the canvas well. The second thick liner was on the trunk side and probably provided both temperature and sound deadening. That insulation was fragile and became a ripped mess over the daily driver years of camping gear and other stuff packed into the trunk. I got so tired of chunks of it falling off or hanging in the trunk that I finally probably removed all of it forty or so years ago.