B-Quiet ultimate first, this damps vibration and seals things so well that if it isn't rusting now, it wont. Then top with either neoprene, I used half-inch myself in the footwells and 1/8 self adhesive from RAAMmat (cheapest price I've found) for sound and heat insulation everywhere else. I also used other products but found the combination of these two was the best results for the investment, easiest to install, and had the best water repelling properties.