If it'* the stuff I think you're referring to, kind of a sticky thing stuck to the cab-side of the steel; I'm not completely sure *how* to get it off, but if you can cut or scrape or chisel it off, I believe the residue left over that sticks it on will come off amazingly easy with ordinary mineral spirits and paper towels. Then, when you complete your repair if you want something to replace that material, I'd highly recommend a product called "Peel and Seal" or maybe it'* "Peel n Seal" -which you can get at Lowes Home Improvement stores. It comes in a roll 6" wide, and costs around $12. One side is a thin aluminum sheet, and the other is an asphalt based damping material. They sell it in the aisle with ventillation ducting and insulation. They don't sell it at Home Depot.
Alternatively, you can buy Dynamat at an autosound store, it is almost identical to Peel and Seal but the backing material is rubber based instead of asphalt based.
97 SE, teflon wiper blades, Dunlop Sport A-2 tires, Leather steering wheel cover, Pioneer DEH-P480MP mp3 CDRW head unit, Pioneer 12-disc changer, iPod hookup, Boston Acoustic 3 way 6x9'*, Boston acoustic separates in door pods, Alpine 4 channel amp in trunk. Magnaflow dual outlet muffler and Ractive stainless tips. Autozone rice pipe and K&N 4750 intake kit. Clear corner lights. Energy Suspension end links.