IGD,
I DID exactly what you are trying to contemplate.
http://www.steelsoldiers.com/cucv/37944-hood-insulation-install.html
I use fatmat, not dynamat UNDER the
LMC Trucks Insulator (cost $62 plus shipping - you need 12 retainers to hold it in place and they are $1 each, plus the insulator at $40 - edit - note that the middle hole in the hood is NOT the correct size, so if you want to put a insulator retainer there you MUST enlarge the hole).
This quiets the engine down almost entirely. I use a
modified intake with a K&N airfilter and that puppy IS noisy, but it does flow air. I recently replaced my mufflers with turbo mufflers so now I have a nice throaty roar from them and now I have good air flow in AND out. It's an interesting sound mix. I'm not sure which is louder, the intake or the exhaust. But it's a sound I enjoy.
Hope that helps.