Of all the things associated with old trucks, rust is on the top of the list of "most common." As time goes on, it won't be surprising to see it as the number one item on the to-do list of practically every fresh truck project. Fortunately, the aftermarket has come to the rescue, providing replacement panels/parts for pretty much every major truck application for Ford and Chevy (time will tell how they respond to Dodge and other manufacturers).
Obviously, Chevy owners have it made when it comes to aftermarket offerings. Simply flipping through the pages of this magazine will reveal that fact, and if you happen to have a '67-72 (long, short, step, or Fleetside), choices are unlimited when it comes to new parts resources, most of which can be utilized from a mail-order perspective. For folks in the Southern California region who'd rather shop in person, Brothers is the ticket. Located in Corona, just minutes from Orange County--gridlocked traffic notwithstanding--the "brothers" Flanders, Steve and Jim, have developed a business that caters to Chevy truck lovers, old and new. From taillights to hubcaps, wiring to patch panels (you knew we'd eventually get to the point), they offer pretty much everything under the sun for '47-87 Chevy and GMC trucks. Moreover, the brothers collectively own a pickup from each era, which they have carefully restored to factory specs. Which finally brings us to the heart of the matter: rocker panel replacement.
We happened by the Brothers compound recently to see the collection of pickups. While there, we were also lucky enough to witness a rocker panel replacement on a '67-72 C10 firsthand, which we obviously didn't hesitate to capture on film for your viewing pleasure. (Please keep in mind that while Brothers offers the products to restore your truck, they're not in the business of installing the parts they sell. This is a company-owned vehicle used to test products.)
If your Chevy or GMC pickup is victim to Mother Nature or road abuse, Brothers has what you need to rid the rot, among other things!
Replacing rusty metal components can be accomplished in a number of ways; the easiest of which is obviously replacing the entire section affected by rust. For areas such as rocker panels, you'll first want to locate the factory spot-welds--do not simply cut the panel out and the seam. With a designated spot-weld drill bit, proceed with removal. | 
When using the special bit, only drill through the outer layer of metal until the spot-weld "pops." Do not drill completely through both layers. The remaining weld is ground off once the panel is removed. | 
The spot-welds don't stop at the seams; look carefully beneath the rocker, too. You'll know you've gotten them all when there's little or no resistance when pulling the panel by hand. |
Don't be too surprised to find even more rust once the old rocker is removed. The Brothers truck faired quite well compared to many others we've seen. Notice, too, that the door has been removed. While not totally necessary, the absence of the door and lower hinge make access much easier, especially when working towards the front. | 
A grinder and wire wheel took care of the surface corrosion on the inner brace... | 
...as well as smoothing out remaining spot-welds. |
Prior to installing the new rocker panel, all bare metal was coated with a primer sealer to prohibit any further deterioration. You could also take this opportunity to apply a spray-on sound deadener/insulation, such as Mr. Gasket's G-Muff, but be cautious not to apply any directly to the areas you will be welding the new panel on. | 
A quick test-fit shows the new panel fits nicely and that no "coercing" is necessary. | 
Prior to welding, a sheetmetal screw at each end of the new panel will keep things in place. C-clamps, fabricator's magnets, or tack-welds are also options. |
Pre-drilled holes provide reference for the upper spot-welds, while the underside can be welded directly to the inner structure. If, however, you also have substantial rust underneath, that must be addressed first. | 
Rust no mo! As shown, C10 rocker replacement is straightforward work. Things get a bit more complicated when you start attacking lower fender and cab corners, but for experienced or adventurous builders, it's nothing a day's work can't tackle! | |