I used the Kilmat product. 80mil 36sqft = $57 on Amazon. It was comparable to dynamat that the PO already had on the floor. That little box was enough for me to do back of cab, replace missing pieces I cut out of floor, all the way up the firewall, and I still have enough to do my doors. Sounds like the perfect amount for you as well since we both had floors done.
So whatever product you choose, 36sqft will be the right amount.
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