Installing new carpets

I used this behind my rear seat on my 68 Hardtop Dart. Not cardboard. Check your measurements. This is 2'x4'. Not sure if you need bigger. You could always spray it flat black.
Handprint 1/8 in. x 2 ft. x 4 ft. Tempered Hardboard (Actual: 0.115 in. x 23.75 in. x 47.75 in.) 109112 - The Home Depot