Right now these questions apply to my 74 Bronco/rockcrawler, but in the nearish future will apply to my 39 Plymouth coupe. I've read a lot of threads here, and other forums, but they haven't really addressed my questions I do paint & bodywork for a living. I've only been at it about 6 years, not a lifetime, so I've still got stuff to learn, but have a pretty solid basis on things. I have my truck torn apart right now. I've been thinking its time to address the horrible heat & noise that make driving my truck unpleasant. I've got lots of access to the firewall & trans tunnel right now. I've read about the ceramic beads & exterior latex house paint option for homemade LS. Even at "blowout" "special" LS prices from our paint supplier, the homemade stuff is significantly cheaper. Our paint salesman told me that LS should be applied to the bottom/exterior of the tub. The instructions from LS states that the best application is to the interior of the truck. My worry about application to the exterior of the truck is adhesion/prep, but also, and more importantly, the potential to allow water to get under chipped or damaged LS & start rusting the floors/tub. I'm going to bedline the interior tub of my truck, but want to add the noise/heat protection. As I've read that bedliner will help with noise, but not heat. The guys at my shop, both with 25+ years in the business, thought spraying the bedliner over the LS would not be the best bet. As they don't know how the bedliner would react or adhere to the latex based LS. They both thought mixing the beads into an epoxy primer, and applying it under the bedliner would be the best. The epoxy primer sticks to paint & metal (it looks like I"ll be stripping my tub to bare metal), and is the preferred base coat for bedliner. My paint rep didn't give me an answer when I asked about applying bedliner over LS. His answer was apply it to the bottom of the tub. I know bedliner isn't an active topic over here, but if anyone has thoughts, I'm all ears. When I asked my coworkers about doing the bottom of the tub, they suggested adding the ceramic beads to a synthetic enamel. It is cheap, catalyzed (tough), and seems to "stick to everything", so it would do well adhering to an old, dirty, greasy tub that might be hard to prep properly. I know 74 Broncos aren't Hamb friendly, but thought the concepts cross over for the hot rods. And I will eventually be doing this to my Plymouth. Basically, I want to know if this stuff should be applied to the interior or exterior of the vehicle, and why. If anyone can lend an opinion on the application of bedliner over LS or beads in epoxy primer, please do. Any input is appreciated.