i did do my pillars, but not my roof, no headliner (custom deluxe). another $20-$30 worth of dampner would cover that. putting mlv or sound deadner on the roof would be pretty useless, not a lot of sound hitting your truck from above. the best gains are by making a "tub" of dampner & deadner from the windows down. personaly i would not spray anything under my truck, (second skin, lizard skin, rust proofer, etc.). on a street truck maybe, but not on a 4by. water & mud will eventually get under it. with 3 feet of air under my truck, heat has never been an issue, even with a big block
fatmat
closed cell foam to de-couple
mlv
fatmat & mlv in doors
i found the best gains were doing the doors, rear pillars & cab back wall. seat of the ears test, i'd say i cut noise by about 70% compared to before (absolutely nothin')