My '92 truck came to me with a plastic bed liner. It's a bit rusty under the liner and I don't know how long it's been in the body. It is handy for one thing, a load handler. A buddy of mine sells fire wood on the side and used a heavy duty Load Handler. Next best thing to a dump body! I picked one up on eBay for $65 three years ago and love it. To use one, the bed must be slippery. They do sell a mat that can be placed on top of non slip liners. Depending on your set up, unloading coal with it is almost
too easy. I put a doubled piece of 6 mil plastic on top of the Load Handler mat that's big enough to go up the front, sides and tail gate before the coal goes in. Unloads in next to no time. Next to nothing left in the truck bed. You can direct where the coal goes by getting a helper to hold the sides of the plastic sheet up as it comes off the tail gate. My bed is a step side, but you can build plywood wings to direct the load around the front of the wheel wells in a normal bed.
Full disclosure ... I don't own any stock or have anything to do with the company. I just like how easy it makes unloading anything. I've used mine with wood, compost, sand, gravel and, of course COAL! Just dropped off a 1/2 ton to a fellow forum member yesterday and this time I let him crank it. Paul Harvey use to advertise them on his show. I'm going to miss listening to him.http://www.loadhandler.com/
Edit: How long has the spray on system been around? Do they chip and come loose? I'm curious if the film behaves like undercoating on the frame does after many years when it cracks and corrosion begins to creep under the film.