How To Replace An Inner Fender Apron

We're following along on the restoration of a '68 Mustang GT fastback. The Northern California car is essentially a rust-free example--except for one particular area. While you might think the Nor-Cal climate could be to blame for the car's rusty inner fender apron, the culprit is actually battery acid.

Likely an issue for many vintage Mustangs, the right-front (passenger-side) inner fender apron is home to the battery tray and batteries that can leak acid. After 40-plus years, the panel in many cars is certainly going to want for better days, which was very much the case for our subject car.

The solution? Replace the panel. While it might look daunting, it's actually a fairly basic procedure that any good body shop can perform. The body shop that helped us out for this project is Julian's Collision Center, which also happens to be the facility that repainted this car in its original Acapulco Blue splendor.

With the fenders still off for the paint job, it was the perfect time to replace the inner apron before reinstallation of the front fenders. But before that could commence, we needed to show up at Julian's with an apron in hand, which we did after swinging by National Parts Depot's Ventura, California, location to pick up two versions of an inner apron.

Not only is the coating already in place on the apron at left, which prevents rust, note also its better-made mounting point for the battery tray. The bare metal version's battery-tray mount is more of a tacked-on afterthought rather than integrated.	Better quality on the coated apron at right is also evident here. The bending and curving of the metal is more factory-appearing, pronounced, and deliberate. The bare one's metal bends are less pronounced, and it's clear that it's not as well made as the coated panel. Also note the bottom hole on the coated panel is a square factory-correct cut, whereas the bare panel's rounded hole is simply a quicker and less involved cut. It was easier to go with the coated apron.	The first order of business was to remove the car's battery tray, which was completely rusted out due to 40 years of battery-acid exposure.
With the battery tray removed, you can see that the apron is toast. Panel replacement is absolutely the only correct way to repair this area of the car.	Removal of the old apron begins by cutting it out with a cutoff wheel, starting in front of the shock tower.	Cutting continues down the side of the apron. Note that the part of the apron that attaches to the shock tower isn't being cut. This is so the tower doesn't get touched. The strip section of the apron that remains attached to the tower will be removed later.
Cutting continues down the side of the tower and along the front subframe. Again, it's clear the body techs at Julian's are doing this right because both the tower and front subframe won't be altered at all during removal of the old apron and installation of the new one.	Further effort to avoid damaging other panels on the car--in this case the radiator core support--is evident by use of an air-powered saw to gently separate the apron from the core support.	After a little more cutting where the apron and core support join at the bottom, the old apron is nearly cut free from the car.
With the panel cut out, it's then lifted out of the car.	With the main apron panel removed, work then commences on removing the remainder of the apron still attached to other panels, including the shock tower (shown here), the radiator core support, and the front subframe. Here, the spot welds that joined the apron at the top of the shock tower are ground away.	Once the spot welds are ground off, the strip of apron still attached to the shock tower can be peeled away.
More careful grinding down of the spot welds continues on the strip of apron that attached to the front subframe.	You can see the strip here that was actually part of the old apron. With the main part of apron already removed, it's been partially and carefully cut away from the shock tower, which avoids damaging the tower.	Further work continues on removal of the remaining strip of old apron. The shop tech is now using an air-powered chisel to gently separate it from the front subframe.
With all of the old apron finally removed, the surfaces to be welded together need to be cleaned up with a sandpaper wheel. Everything on the car where the apron attaches is thoroughly cleaned, including the shock tower, radiator core support, and front subframe.	Though the various pieces that attach to the new apron were in good shape, some minor shaping and straightening was required, which was easily done with a shaping hammer.	Preparation of the new apron begins with a series of small holes drilled in the edge for the spot welds to attach it to the car.
With all the holes in place and each one scuffed clean of the black coating, the apron is then test-fitted to the car.	Before spot-welding, the apron is temporarily screwed into place in about four locations, which will locate it for the spot welds.	Once the spot welds are completed, they're smoothed down with a sandpaper wheel until the line of welds becomes invisible and the strip where the apron joins with the shock tower matches the rest of the apron surface.
Every hole that's been drilled into the apron gets spot-welded. The welds start at the top of the shock tower, then run down the side and across the subframe.	To complete the installation, new holes are drilled to match those in the coil-spring cover. The existing holes in the cover are used as a template.	Here's the installed apron from inside the engine compartment. It's ready for surface preparation, painting, and a new battery tray. A shop like Julian's can do this sort of metal removal-and-replacement work quite easily. This project was complete in less than three hours.