Floor panels (pics)

[Bootsy]

I did the same thing to my 79 a couple of years ago. First of all, don't use a roofing underlayment like Ice and Water Shield, the melting point is too low, remember the exhaust pipe is inches away on the passenger side. Use a butyl based sound/heat protector with a higher melting point than the bitumen/asphalt based materials. I echo the other posts praising POR 15, it's fantastic stuff, I wouldn't use anything else on the floor or trunk area.

Good luck.