[mr48chev]

I'm thinking along the lines that Parkwood said he did in post 2 and that is use Lizard skin and then use a sound deadening mat material. And there might be a layer of peal and seal in the mix.
I've had my truck since 1973 and we have suffered through heat and noise on a number of long cross country trips of thousands of miles and don't plan on suffering on the next several thousand miles. It was part of the deal when my wife and I were in our 20's and 30's but now that we are in our mid 60's the comfort of AC with windows that actually roll up and insulation that keeps the heat and noise out sounds pretty good to us.

Sound wise I'd search out what the big sound contest guys are using to keep the sound contained. Heat wise I think the guys here have pretty well nailed it from what I have found in my searching.