JOhn - I usually use Cascades Audio products, as they seem to be the only ones who have even a basic understanding of acoustics. Dynamat may also but are not responsive to questions (and I ask them as Dr. Webb, not some bozo with a thump head audio fixation).
You can see some pics up above of what I did to the front and sliding door.
There is some sort of chewed up foam conglomerate under the carpet right now. Not sure if I will remove it or not. I will test the panels for resonance and install a butyl rubber bases sound deadener on any that resomate (~~25% coverage is all that is needed). After that, I may put down a layer of so-called Mass Loaded Vinyl (MLV) - Constrained Layer Dampening (CLD) which they call
VB-4. Their
VB-3 is for areas where you need to turn a tight angle but costs (even) more.
The thing is -- we have a rear-enegined vehicle with rel. poor air flow management ("aerodynamics") -- that means that maybe I want to put the
VB-4 over the rear engine compartment and the sloping bulkhead in front of it where the box under the Z-bed rear seat is located (I already used some sound deadener scraps for that sloping area). A 4 banger VW motor noise is not what I really want to listen to on a trip - my neighbor says he loves it tho...
Then, see what I can do re wind noise and rattles.
Doing the front floor might be the last thing to do, tho I'm not sure. Certainly, tire noise is an issue on this vehicle, tho it is not clear to me whether it is entering the cabin via the window glass or via the suspension. New tires will help, but I need to retain some off-hwy traction ability and that often compromises noise reduction.
Also, I put sound deadener and some felt on the interior of the front sheet metal when I had the dash out a couple of years ago.
Feel free to post any further questions or to drop by on one of your jaunts down I-5. I am just a few minutes from a major I-5 junction.
How is your conversion running?