I used Noico 80 mil from Amazon. It's Butyl, like most of the high end Branded stuff, but any butyle product will work. I covered everything including inside the doors and under the cowl. Of course it was easier because I was building the Bronco. That was for sound with a a bonus effect on heat. For the heat I also covered it with Noico foam cell 180 mil for some sound but mostly for heat. Any amount on the floor and firewall will help but since I was disassembled, I went the extreme. The pix are the Butyl. I don't have access to my foam cell pixs at the moment. It took a little over 36 sq/ft to do that level of coverage. I also used a metal roller that had groves in it to make it easier to see where you had already pressed the butyle in as it left marks on the foil. I used scissors to cut pieces to match but the butyl sticks to the blade. I also layed the sheets out in the sun for 30 min to heat them up first. It made them way more plyable.
