while it's apart, you may as well deaden the whole thing, and if you're feelin spunky pull out the seats, carpet, and headliner and do the entire truck. you'll notice a big difference doing the entire interior, especially with road noise. if you just do a little around the speaker, i doubt you'll notice any differenceat all. and if you plan on adding bass, definitely deaden the roof. chevy's are notorious for the roof flexing like hell when you put a significant amount of bass in there, and if you pull the headliner down and see how flimsy it actually is, you'll see why.