Cleaning up the interior of my 1948 cab. Looks like at one time there was some sort of waffle material attached some how to the interior roof surface. Just curious, but was it some sort of paper product adhered to the roof. I am thinking to putting sound and heat mat on there, then the headliner. Should I just prime the surface and then put the mat on, or is the mat better on bare metal?

A day without laughter is a day wasted- Charlie Chaplin
When wrestling a grizzly bear, you have to keep at it until the bear gets tired, not when you get tired.
1948 Chevy 2-Ton