Just finished adding sound deadener to the interior of my new-to-me 1986 720. I am very pleased with the difference in road and engine/tranny noise and it was a pretty easy job - although time consuming at first.
Long drives were really difficult with the noise and the truck didn't have a radio when I got it and once I had one installed, it was almost impossible to hear on the road.
Decide to look into adding sound deadener and settled on the Kilmat 80 mil butyl/aluminum underneath the Noico 170 mil green which is a closed cell foam with some kind of more dense foam layer and adhesive backing..
Kilmat's Amazon listing looks exactly like Noico's so I assume that both are made by Noico but the Kilmat was slightly cheaper. I bought the 36 square foot version of both and ended up with 2 sheets of the 80 mil and 3 sheets of the 170 mil after doing the floor, door pillars behind the seat and the panel behind the back seat. I haven't done the doors because I am waiting for some door parts to arrive and I don't know what the doors look like with the panels off but I assume that 1 sheet of the 80 mil if cut up and spread around will be enough for each door. I'll add the 170 mil on top of the 80 mil and will have enough for each door, I'm sure. I am also sure that once I do the doors, it will be even quieter.
After doing a lot of research, I decided to use both the 80 mil and the 170 mil in combination because the 80 mil is only for reducing vibration in panels and the 170 mil is for sound and temperature control. I didn't test drive after installing the 80 mil (mainly because the seats were taken out) so I have to assume that adding the 170 mil did more than 80 mil by itself.
Rumor has it that the 80 mil doesn't have to be fully cover the panel (a few youtube videos I watched said that 50% coverage was acceptable) and you are supposed to tap on a panel and if it sounds tinny, add a piece of the 80 mil and tap various areas of the panel until the panel sounds, for lack of a better word, dull. I decided to go for full coverage since I had already paid for the 36 square feet and also because I didn't want to do it twice if the 50% coverage didn't help.
It took 2 solid days for the whole application but I lost a lot of time doing the 80 mil trying to finesse the cutouts so the 80 mil perfectly fit over the items that aren't supposed to be covered like bolt-holes. I evolved to cutting a rough opening for these items after a while and it went a lot faster. I am sure I maintained 95% coverage even still.
The packages contained instructions which just boiled down to cleaning the area before installing.
I found that cutting a manila folder so it is the same size as a sheet of the material was a good way to quickly make patterns. For some of the pieces that needed to be arced to fit an area, paper towels worked well because they are flexible enough to push into the irregular areas to trace the outline. I purchased a roller with the material and used it on the 80 mil but smoothing the 170 mil with my hands was more effective for that material. You can reposition the material when installing as long as you don't press it down but to keep it from sticking before I wanted it to, I found that folding back the release paper about halfway made it easy to stick it down on one end and then pull the release paper out while smoothing it down. These trucks have tons of ridges, etc on the them and you have to allow for the material needing to be cut longer than you think because it has to negotiate all of the ridges and valleys.
I think with the roller, it cost maybe $140 - $150 to do this. I would say that it is well worth doing if like me, road noise was wearing you out on those long drives. Kind of a double-edged sword because now I can hear that my throwout bearing - or something in the are of the clutch - is making noise.