I used Eastwood's Thermo coustic. It's the same thing as Dynamat at half the price. I tried the construction material but it didn't compare and didn't stay stuck. I also used a 1" thick closed cell carpet underlayment on the floor under my carpet. It's designed as a sound barrier for homes and works great in the truck. The use of a cloth seat or seat cover makes a huge difference as does covering the cardboard headliner. Noise is still going to get in but it helps to reduce the hard surfaces the noise will bounce off of.
Replace the rubber parts of your cab mounts! That made a HUGE difference in my case.
Even after all of this I still wear earplugs on long trips. It's the cheapest and easiest soundproofer you'll find
