I think the above is accurate. I have a '68 convertible Barracuda. I put dynamat extreme from the front windshield down to the rear trunk divider, and then covered that with the double, foil-sided jute mat on top of that. I seal the seams with that wax paper covered aluminum foil duct tape. I use it to hold down the edges too. I put strips of dynamat inside the doors and under the door panels too.
Make sure you have good seals in the doors and elsewhere too.
The combination of the 2 works very well to block fumes, sound and heat. It is a convertible though, so I didn't put the jute mat in the low spots where water can pool if it gets in. It usually does no matter how well I try and restore the factory seals.
As far as the trunk goes, I won't use factory style rubber mats because they trap water from condensation and leaks resulting in rust eventually. The top boot is just a thin material, so sound passes through it from the trunk area easily. I never hear much from that, and the cabin and door insulation does help. I do have one I can install for car shows etc.
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