I would coat the floor and behind the seat area with SEM RUBBERIZED UNDERCOATING Part #39523
You may also shoot it inside the doors once you gut them, this prevents the truck from sounding like a tin can
new cab mounts also help reduce the squeeking, and brand new quality door and window weatherstripping reduces whistling noises
https://www.semproducts.com/product/...rcoating/39523