I have a 1967 Coupe, been in my family for 47 years. I recently changed my rear shocks, removing the back seat to do so. The underlayment has disintegrated, leaving this black tar like like residue. I'd like to remove it before installing the replacement. Hoping for suggestions as to how to get it off. It's like dried black glue. I shudder to think what's under the carpet once it's removed.