I did the whole interior of my '97. Next to the Hurst/Core shifter, one of the best things I've done to the truck!
65-70% of road noise comes from the doors.
On the inside of the outer door skin, I did 3, 6" wide strips of 'FatMat' followed by a second layer that covered the whole skin.
Doing the 3 strips first helps to kill any panel resonance. Always do an uneven number of strips. 3, 5, 7, whatever.
Then that stupid 2nd panel in the doors was covered on the outside. (Don't cover up those vents in the bottom of the doors!)
This was followed up with a 3rd layer on the inside of the plastic door panel. My door pins hate me!
I did the roof the same way. 3 strips followed up with a full covering.
The floor has the strips, (3 on each side) then a full covering, followed up with 2 layers of 1/8" closed cell foam. 2 layers because it forms to the floor better than 1 layer of 1/4". This has the rubber flooring with the underlay over top of that.
The back wall was once again done in strips first (5) with 2 layers of FatMat, & a layer of 3/8" closed cell foam, followed up with the factory carpet.
I also put a layer of the FatMat under the 'A' pillar plastic.
What a dif! No more random creaks & rattles. Heater seems to be more efficient. Stereo sounds way better! The truck feels more solid rollin' down the road. @ 60mph., I can have a Harley beside me runnin' shotguns, roll up the windows & I can carry on a normal conversation.
Like I said, one of THE best things I've done to the truck!