IMO,

I'm going original as much as possible. In this case, I will look for an OEM original solution to the sound deadening material to apply to the floor.

I had my under carriage sprayed with foam back in '81. It dropped the noise level a lot. Especially in the wheel wells. However, the installer plug my rockers etc. and water was unable to drain properly. I kept my car all those years, hoping to be able to restore the car again some day. That day came about 7 years ago. I started restoring the car and what I found a lot of rust held together by foam coating.

I see the peel and stick insulation as almost the same as the foam coating in that water could be trapped and thus erode the body with rust again.

However, other people that have and will use the peel and stick without issue. I live in the north and water is an issue. These cars sweat and rust in our garages!

The other reason for the insulation is to reduce the heat transfer. That is only an issue on the firewall for my location. So I'm not concerned about the heat.

Loud stereo trumps engine noise. I will just turn up the volume to counter the noise! lol

Anybody know where to get the old style stuff for the floor?