Another sound and heat insulation option that I DIDN'T see covered on here is special carpeting set options from ACC.
ACC offers both a "mass backing" option that adds a 45 mil thick Ethylene Vinyl Acetate backing to the carpeting, but it only gets applied to molded pieces and not die cut pieces like flat cargo and side panels.
They also offer a carpet set pile upgrade that they call "Essex Plush", it includes 40% denser carpeting pile and is 3/8" thick instead of 1/4" thick so again provides additional sound deadening and heat reduction vs. standard carpeting pile.
For my 79 C3 I'm going with 3 layers of interior sound and heat reduction:
1. The 80 mil Kilmat sound deadener
2. A 3/16" thick, aluminum backed closed cell foam (From "VetteNuts" who sells pre-cut kits for most Corvette generations)
3. The ACC Carpet set with the mass backing and "Essex Plush" pile. -I shopped every major Corvette supplier's best Christmas sales and special coupon codes in Dec 2020 and the regular everyday price at RockAuto beat every single one of them, for what that's worth.
On the exterior of the car I'm going with WisAuto Aluminized stick-on Heat Shield sheets on the firewall, AC evaporator box, under the foot wells and part of the trans tunnel.
https://www.amazon.com/WISAUTO-Aluminized-Thermal-Barrier-Adhesive/dp/B07R6F97C9 -I know some folks go with the Lizard Skin ceramic paint in those area, which seems like a really good option.
The AC Evaporator boxes tend to get forgotten but some C3 folks will go to exorbitant lengths to get cold AC and the passenger exhaust manifolds/ headers are sitting right next to the AC evaporator box, so it seems like the perfect place for a heat shield that reflects back that radiant heat.
I also have a transmission tunnel foam collar that blocks engine bay heat from migrating into the top of the trans tunnel.
Image showing the thickness difference between standard ACC Carpet pile and the Essex plush:
In my life I moved from the quiet of Indiana cornfields, to the quiet of a small town in Ireland (although we had fog horns and a commuter train), to the constant barrage of noise that is living in a Seattle suburb so for the past 3 years I've been adding lots of noise reduction to my life wherever I can. Quiet appliances and noise reduction products (I even applied noico panels to the inside of my washer and dryers panels; I put my garage air compressor into a garage cabinet and covered it's walls with sound deadener products, mass vinyl sheets in the attic over the insulation, etc..). I love the sound of my Vette but I want to cancel out the annoying sounds and get rid of the footwell inferno. I'm hoping my efforts pay off.
Adam