It is much easier to repair a falling apart Dearborn firewall pad for the reasons and methods Jeff explained about doctoring a repro pad. You can glue together parts and blend them in with the body Schultz type products and end up with a superior looking part. If you have all of your pieces I would encourage you to try and repair your original before resorting to the poor repro pads. Remember the back side that faces the firewall can be the material canvas, burlap etc. that you glue to because if trimmed properly it will not be seen once installed.