I did a bunch of research online and compared product quality with cost and overall effectiveness when choosing a sound-deadener material for the FLOOR of my car. I will later be doing the inside of the door panels and the rear wheel-well areas another time, but for now I wanted to only tackle the floor. I went with a product called RAAmmatt 60BXT. I got a great deal and was able to cover the entire floor 1 1/2 times. (the 1/2 time is where i doubled up the layers on the transmission tunnel and driveshaft hump because those areas are noisy. Now, let it be clear that I am NOT trying to make this car sound proof with the windows closed because that would be silly. My goal was to use the sound deadener to reduce the road noise, mini squeaks and rattles, and the noise that comes from the rear end gears. This product worked great and was super easy to install. There is really no science to it, just cut a piece, fit it up, when it seems to fit good, peel the material off (to expose the black sticky side) leaving the shiny side up, press on, and rub/press the material down. You can overlap areas and cut it to whatever shape works. You have to think ahead and also cut out holes in the material for anything (bolts, wire clamps, seatbelt holes) that will need to accessed later, but thats easy.
Since I had the interior out and did the rustproofing, sound-deadener, subframe work..... I had to pull out the original carpet. It was faded from 23 years of use and sun so I gave it to a buddy who needed it for his camaro. I ordered a new passanger compartment carpet from 1A-Auto for a good price. The measurments and curves were spot on. It IS an ACC carpet! Below are pics of the install, which is straightforward, but you have to cut holes in it for the seatbelts, seat mounts, and around the area of the center console. Cutting through the carpet is easy, but cutting through the fabric backing/padding is aggrevating. In some pics the carpet looks grey due to the sunlight or camera flash, but it's actually a solid rich black color. Now that the carpet is in, I was able to toss in the rear seats, neatly run the wires for the sounds system (and install it again), and regroup other wires in the transmission and stereo area to be much neater.
... now im just waiting on the driver's seat to get a few areas patched so i can put it back in and drive the car all over for the next 6 months