If you're looking for something to cut down on road sound entering the passenger compartment from the trunk, I have heard that you can take a piece of cardboard cut it to fit behind the backseat and tape it into place with metal duct tape. then buy duct insulator from Home Depot or Lowes and cover the entire piece of cardboard with that. I hear Frost King is a good product for this use.
1967 Coupe, after market 302, AOD Transmission, Manual Drums all around and a brand spankin new Holley 600.
"Power corrupts. Absolute power corrupts absolutely. But it rocks absolutely, too."