[JLMounce]

Dynamat makes custom cut templates for the entire f-body, which takes out a lot of the guess work. To do the entire car, it ends up being about 1400, so it's not cheap. There's parts of that you can get away with not doing however. You don't need to do the trunk lid and the trunk pan itself is less of an issue, especially if you have the jute backed divider. If you're not running powerful speakers in the rear deck, you can also get away with not doing the package tray.

This also kind of goes for the doors. If you're not running speakers in them, you'll gain the most by making sure that they door weather strip is in good condition as well as the door card and the window felts. Most of the noise from the doors is coming from loose crud inside them, the window not being contained properly by the felts etc. Second Skin makes a good spray on constrain layer that is easier to work with should you wish to do the inside of the door and you can add a mat product under the card for more if you want.

It does kind of sound like you're going for a more cadillac type experience, so I would focus more on the decoupling layer and mass loaded vinyl layer in strategic places. You'd want to do the trunk as well in that situation.

This isn't part of the insulation package, but another area to address is the nuts and bolts of the car itself, literally. Spend an afternoon with the wrenches and sockets out and put a cinch on any nut/bolt you can find. A lot of NVH comes from stuff just not being completely tight and rattling around. You'd be surprised how much more solid the car feels after doing that.