I'll be swapping a new interior into my '79 crew cab soon, and I'm planning ahead for anything that could be done for road/engine noise reduction at that time. The truck has had the body completely re-done, but the interior is still "25 year old farm truck". I have almost everything from a wrecked crew cab - seats, carpets, door panels (four complete doors with PW and PDL), all the plastic trim, weatherstripping, etc. Is there something I can put in the doors/on the floors to cut noise and protect from rust? Just the typical spray can undercoating, or something better? It is fairly loud now on the highway with the Cummins (no muffler) and 4.10's, bad & missing weatherstripping and rubber floor mats. I'm sure that just installing what I have will help a lot, but I'd like to make it as quiet as possible while I'm doing it. I like hearing the Cummins roar, but I want to be able to roll up the windows on a long trip, turn on the AC and have it quiet. Any help would be appreciated.