Iinstalled the same mat, but first I put in a product from home depot (like dynamat excepts lots cheaper, then covered that with a simalar material that is closed cell foam with aluminum outer coating --duct insulation. To keep the original look I put a new stock rubber floor mat on top of the rubber mat. My truck is quiet as a church mouse. no heat comes through the firewall. it was well worth the work. Kieth
here is a picture-----http://kieth.smugmug.com/Trucks/66-GMC/13311086_xjDHcV#!i=1438205345&k=QRXTmdg&lb=1&s=XL
