sound deadener

On the front floor-firewall area, you want to block both sound and heat. Inside the doors, just sound. For sound-blocking, it is most important to add mass in the middle of the door panels, so it lowers the "drumhead" frequency. There are several vibration modes, but the main in-out motion of the center is the biggest one to stop. Ditto for the roof sections. It may also add some damping. For longevity, butyl rubber is probably best. Asphalt products will slowly turn hard, as you see in the stuff the factory used in the 1970's. The foil w/ foam rolls at Home Depot are good for blocking heat, like above the headliner, but you still need to add some mass in the center of the panels to keep quiet. Even a 1 ft x 1 ft square should help. The aftermarket stuff like Dynamat is very expensive, so the post above of Home Depot sticky stuff for $20/roll is helpful.