For dynamat type materials, 25% coverage gives 90% of the results. This is what will save you money, not buying a cheaper material. Going nuts and covering the whole panel is overkill, and is just adding weight to the car. Tile a couple 1 sq ft pieces anywhere you see flat expanses of metal. Metal with stamped shapes into them are inherently stronger, and need little to 0 dynamat. Same goes for metal that bends, or attaches to a brace or a panel attached at a different angle.
The biggest problem is that dynamat only damps vibrations through long flat expanses of panels (think outer door skins). It does little to nothing to block low frequency noise (think 70mph up the highway hummmmm) contrary to popular belief.
Low frequency road noise is best blocked by a dense material such as MLV (Mass loaded vinyl) or a lead barrier. Lead not being the best for automotive use, and harder to come by, I'd say MLV is your best bet.
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Peel and seal or home depot roofing material is asking for trouble. This stuff gets soft and run's/melts with heat. It tends to have that asphalt smell as well. It is not intended to be an automotive product. At the very least, it stop's adhering to metal when heated. Avoid it at all costs. It's similar to using dryer ducting for your intake. Maybe it works to a degree, but there are much better solutions.
To sum this up, use dynamat on outter door skins, quarter panels, behind 6x9's, and on the roof, floor and trunk area floor w/ 25% coverage being all that's needed. Then apply a layer of MLV to the floor under your carpet, and watch how much quieter your car will get.
Unfortunately this won't eliminate all the rattles, but some felt tape, strategically placed foam, replaced panel clips, and a little creativity will get rid of most or all of those.
F-body's don't need to be noise boxes, and even the guys who don't care about music in the car can enjoy a quieter F-body.
