Up to this point I've not told you how to prep the new gutter and roof skin panel: First off when you get all your welding/patching done in preparation for the installation of new parts take a wire wheel, (or sandblaster) and clean/remove all the loose scale, and flaking corrosion. Then when all steel shows a light silver face weld your new drip rail to the cabs newly repaired rear panel. With this welding finished it is a real good time to paint all the bare steel with a corrosion inhibitive paint such a "POR-15". After drying, I then take a 3/8ths inch thick "Scotchbrite" disc and clean/remove the "e" coat from the upper horizontal portion of the drip edge to bare steel. Then place the prepared roof skin on top of the cab, align and clamp with a few sets of "Vise Grip" pliers, and get busy with the welder. As far as heat setting, you barely want to see deformation of the bottom of the drip edge horizontal area and a good melt into the upper area of the roof skin. If you plan to weld the parts only then you will need to drill or punch a series of holes about four inches apart on the flange area of the new roof skin. I use 1/4" and have a pneumatic punch for this. 3/8ths will work but is a lot more welding and grinding to finish. You must also have holes in the drip rail to weld it to the cab panel. This is called "plug welding". I have a spot welder that works from both a single side, and double side with a squeeze clamp but I still prefer to plug weld as it is much stronger. In an earlier post I addressed the glue and screw method and it will work also but is not my preference. Hyman Auto Supply, (based in Chicago) is the parent company of Specialty Paints whom I use for my vendor of the RustFire/RustFree products. If you have trouble give me a call and I'll send you up my applicator gun, and a gallon of the stuff. I don't think it comes in spray cans as I've never seen it. I use the undercoating set to apply it. Rob