The factory Mopar fuel tank pads from the 60's and 70's cars were made from "brown asbestos felt" manufactured by Armstrong Industrial Insulation. Yep, this is the same company that is now Amstrong Flooring. The whole asbestos thing cause them to file for Chapter 11 bankruptcy protection. Their logo, a capital A inside a circle, was stamped in white on the tank pads. 
The brown asbestos felt was also used on firewall and kick panel insulation pieces. It was usually 3 layers of .080" material that used tar as an adhesive. The 3 layers were then run through a roller embossing machine to apply an "indented" pattern to lock the layers together.

I'm working on having a very similar "looking" material made with the same indented pattern for the firewall insulation. The tank pads were either a smooth .080" material or had a very light "waffle" pattern.