The biggest challenge with the older trucks is really the ROAR OF THE 22R-E (spoken in the tone of the Dos Equis man - LOL!). I wish I had applied some thermal-noise insulation on the engine side of the firewall when my engine was being rebuilt. However, it's still possible to add more on the cabin side. A hood insulation may also help. Then extra weather-stripping on the lip of the door frame for wind noise.
Wanna replace the existing edge trim with this...



LOL!

There's really no need to use more of the vibration-dampening. That's all the mastic/tar/rubber is for - to minimize metallic vibration from the panels. Once you have some there, that's good. More will get you diminishing returns for your money.
Better to put the additional expense on insulation - to keep remaining noise from getting into the cabin. For example, even with vibration dampening on the metal body panels, there would still be noise coming from the rear wheel-well. That noise is already inboard of the metal body panel. That noise would still transmit through inner body panel to the cabin. Putting insulating foam on the interior body panel would prevent that noise from entering the cabin. A conservationist, minimalist with a low budget, I'm in the process of gathering packaging foam used for shipping delicate equipment (approx 3/8 to 1/2 inch thick), and I stick that in the back of the interior body panel = insulation at zero or low cost.

 

agree on all above points.

i'd been looking for good weather stripping like that. thanks for that. it looks better than the 3m stuff i'd planned to use.

 

It's made by trim-lok. (https://www.trimlok.com/rubber-extrusion/trim-seal/specialty-trim-seal/109b375b3x316e)
This looks like its wholesale website, but I'm sure we can buy smaller amounts somewhere.
The website can help us find the size we want.