I just installed a new headliner in my 70 H code 340 Swinger, 4 speed, it needed a replacement. I picked this car up last November. It has a black vinyl roof and I wanted to reduce the heat coming from the roof on hot summer days.
So I installed Dyamat to the roof underside before the headliner went in. There is a bonus too, it made the roof less tinny sounding, and it will help to reduce road noise too. Win-win situation, I think.
