Old trucks are supposed to rattle somewhat. Part of the package. Having said that though I stopped a major source of rattling in my PW crew by replacing all the window runs. I can actually hear myself think in it now. No radio so that is my only enternainment. Not for the faint of heart.
Next up is my window runs, disintegrated ones definitely add to the noise. My truck was pretty darn quiet until I simply touched those upper rubber bumpers and they fell out. That left a huge gap so I wedged the broken ones back in there until the new ones arrive for LMC. Guitar from reading your recent post I think some of the noise in your truck is from the back seat springs being worked
I just added a nice Kenwood single disc stereo under the dash, no hacking, leaving the original radio mounted in it's factory spot. Now I can listen to Willie, Merle, Waylon and others instead of myself singing.
