I used KILLMAT on mine. Look through my thread. I did the same to my 64, but with the rear floor pans. I painted mine with a couple of thick coats of Rustoleum and them put KILLMAT on top. It rides so quiet, you cannot even tell it has an engine in it. I don't have to turn the radio up loud to hear it at all and can hear my wife talking to me.....and I'm hard of hearing.
1964 Valiant "Get Runnin & Drivin"