Sound Deading, and in cab rattles

I have 2, 2015 Day cab Coronados with 12.7 Detroit's and 13 spds.
Air ride front axle, rear suspension and cab.
Both are 600,000 mile trucks.

Rattles, vibrations, and noise seems to be getting worse by the month.
No engine, drive train or tire problems.
1. I am thinking of replacing the rubber floor covering. It's got cracks and the insulation looks crushed.
2. I am thinking of removing the ceiling and behind the seats interior and installing the stick on sound deading material and reinstalling the interior.
3. Removing the door interior panels and adding sound deading material too.
4. Both battery box lids rattle bad. Has anyone changed the way these latch down?
5. Thinking about taking the entire plastic snap together dash apart and adding sound Deading material to all of the pieces and frames to stop noise.
Has anyone tried to reduce the noise on these trucktruck? The old 1990s FLDs with 2 million miles are quieter to drive than these Coronados.
Just asking if anyone has and any suggestions.
The materials won't cost that much. And my labor is cheep on the weekends.
If I can make it better for my drivers I want to do it.
I have replaced the driver seats and getting the leather steering wheels reconditioned
The trucks are in very good shape for their age, but are getting noisy to drive.
I would appreciate all suggestion. Except, "what did you expect? You purchased a Freight Shaker" ......dont need that. I know what I have, I just want to spend $ and my time to make them more comfortable.