I have always insulated the heck out of my old cars,covering almost the entire interior of the car. I,ve always like the(quiet)as if it was your family car. In the past I used 3/8 to 1/2 inch thick,fabric filled, foiled covered with a adhesive backing. I was always pleased with the outcome ,how quiet the car became afterward. Now this is no longer used or desired,a insulation 1/8 " with a tar like adhesive. I realize there is a reason for this,cuts down vibration which creates noise,kind of a physics thing. Well my own view it,s not as quiet as the old stuff. the best stuff I ever used was for a old 40 Ford .Insulation was 4X8 ft aircraft insulation 1/2 " thick.