Rust happens. For GM A-body cars like the Chevelle, Buick GS/Special, Pontiac GTO/ Tempest, and the Olds F-85/Cutlass, the Achilles' heel is the lower rear window channel that leaks, dumping water into the trunk floor where it quickly turns to cancer. Our '66 Chevelle rusted exactly where all of these cars do, right at the base of the left rear wheelwell. We called Original Parts Group (OPG) for help with a stamped-steel replacement panel. OPG offers three separate panels for the entire trunk floor for either the '64-'67 or '68-'72 cars. The company also offers a cleaner, one-piece panel that eliminates much of the welding for just the '68-'72 cars. For this job, we needed only the left panel, a few cutting and chiseling tools, our Craftsman 110-volt MIG welder, and a free weekend. Now all we have to do is find that hidden sprinkler under the back window.
 Replacing oxidized sheetmetal...  Replacing oxidized sheetmetal is part of the game with old musclecars. After pulling the junk out of the trunk, we determined that we only needed the left panel from OPG to repair the Chevelle. |  The burly kid in these photos...  The burly kid in these photos is Graham Smith, Jeff's 15-year-old son working on his own '66 Chevelle. We removed the gas tank to prevent damage and to avoid setting the shop on fire. Next, we scribed a cutline inside the replacement-panel outline and cut out the old floor with a saber saw. |  Be sure to not cut through...  Be sure to not cut through the left-side gas-tank mounting brace and the original trunk floor brace (shown) near the wheelwell. Both were in good shape and did not need to be replaced. |
 We peeled back the rusty sections...  We peeled back the rusty sections at the cutline and used a hammer and chisel to carefully cut the factory spot welds. You can also use a drill bit to drill out the spot welds. We chose to chisel them out and grind the metal flat with no holes to fill later. |  With the rusty floor section...  With the rusty floor section removed, we cleaned the rusty areas with a wire brush on a drill motor to remove the surface rust from all the remaining areas. Then we spray painted the trunk-floor reinforcement panel to prevent further damage. POR-15 is an even better idea as a rust inhibitor. If you must replace the reinforcement panel, consider tacking it in place before final installation of the floorpans. This will save time later. These will require overhead welding, which is a difficult skill to master. |  If you are an accomplished...  If you are an accomplished fabricator/welder, you can custom fit the panels with butt welds that will leave a near factory finish. We're sheetmetal hacks, so we decided to trim the replacement piece and overlap the panels. Then we used sheetmetal screws to position overlapping panels together before welding. Overlapping panels are easier to fit and weld but require more finish work. |