I've been on a quest to quiet down my '80 and used "sound and vibration damping sheet" from McMaster Carr, pt # 9709T39. MUCH cheaper than car audio stuff. I used less than three sheets, which set me back about $60 with shipping. They ship fast too, from Sacramento to Chico, I had it on the 2nd day.
I did the doors, floor,rear and any other flat surface in the cab. It definately made a difference, the doors close with a whunk, not with a clank. I still need more in this old truck though... suggetions?
