I did this when I redid my interior. I put the Peel & Stick on the floor, back wall and on the ceiling, before putting the headliner back in. This is what I did:
On the floor, I had quite a bit of FatMat left over from a previous job. It wasn’t enough, so I got some Peel & Stick from Lowes. It is pretty much the same stuff as the FatMat, just cheaper.
Then put the original Tar Mat, from the factory back down. Then put a layer of jute backed foil down. I got this from Home Depot online. Use foil tape to adhere the edges to the floor, and on the seams.
https://www.homedepot.com/p/UltraTou...1406/100656748
Then the new carpet was put down. It also had jute backing. The back wall, I put the cardboard tool tray in and put Amp/speaker carpet on it. I believe it has made the cab a lot more quiet. When I first got the truck, the cab was so noisy, you had to talk pretty loud to be heard. Plus the floor doesn’t get hot around your feet, like it did at first.