1969 Dodge Dart - Carpet Underlay

As @Demonic mentions, the ACC carpet uses shoddy padding in the areas that the factory carpet used a padding. The shoddy padding is not quite as thick as the original jute style material, but you can purchase extra material as @Demonic links. The other thing to think about if your looking to purchasing new carpet is to order it with "Mass Backing". This material is used on the new car carpet kits to reduce noise and temperature variations. It takes a bit more effort installing the carpet and is a bit more expensive, but it works well.