Hi Nate,
It was close to next on my list, so I just removed my gas tank today.
Item A in your picture is exactly how my car is. There is nothing covering this surface. There are a couple of small pads bonded the metal at the upper edge (just out of view in your image) that cover the back-side screws for the voltage regulator and coil.
Item B in your picture is a pad that is similar in construction (and thickness) to item #2 that just drops onto the floor (was not glued down. It is shaped to fit precisely onto the floor metal.
Item C in your photo is a matt similar insulating to #2, but is only 1/4" thick at best. It seems to be two thin layers of the hard tarpaper card with a thin layer of (now disintegrated) grey foam between. This pad is glued to the body as is #2. Sound insulation I guess.
I hope that helps,
Mark
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