It's a common problem that many have already had to or will have to deal with-rust. Let's face it, short of finding a car stored in a climate-controlled garage, any Mopar project we try to undertake is going to have some rust somewhere. But it's usually just a simple matter of contacting the appropriate restoration supply house and getting the parts needed. What if the afflicted area doesn't have a replacement piece of metal available? Let's take, for instance, the driver-side inner front fender of our '70 Super Bee. The battery tray mounting area had a fairly large rusted area brought about by many years of battery acid slowly eating away at it, and no replacement is available. We can either weld a piece in where the rust is apparent, or find either a nice panel at a swap meet that has been removed from a donor car or hope to find a N.O.S. panel at the same swap meet.
Luckily for us, a N.O.S. panel came with the deal when we bought the car, so now all we needed to do was to remove the old one and weld the new one in place. Sounds simple, right? Depending on your mechanical/body repair skills, you might consider it an easy task. Let's say you have found a good, used inner fender at the swap meet, and you bought it. You now have an idea of what it takes to remove the one already on your car. Each of the little holes drilled around the edge of the panel is not a bunch of holes that some dimwit just decided to place on the panel. Nope, those holes are where the welds used to be that held the panel to the car. You will need to do the same thing to the panel currently on your car. to find the locations of all those holes, simply look for the dimples around the edges.
From the factory, the inner fender is welded to the body structure by "pinch welding." an easy description of that process is to picture two long metal fingers, one is touching the inside of the panel; the other is touching the structure outside of the panel. An electrical current is now sent through the "fingers," and the two areas directly under the finger tips are fused together-instant bondage. When it comes time to drill the welds, here is where the first of your specialty tools comes into play. You will need a spot-weld cutter. A spot-weld cutter will cut the area that has been welded, and makes the panel come loose from the structure without drilling through the structure itself. After you get all the welds drilled, all you need to do is clean up the structure with a grinder, and you're ready to place the new panel in the car.
Since we are not a large body shop that just happens to have a pinch welder handy, we'll have to attach our panel with a "plug-weld" system. A plug weld is nothing more than a hole filled in by welding. It may take a little work to make a plug weld look like a pinch weld, but what else are we to do? Remember, we had a N.O.S. panel to install that didn't have any holes already drilled in it from removal. So, first we needed to make all the required holes in the new panel so we could weld it to the structure. Another thing to keep in mind is, you simply cannot weld the inner fender on without taking some measurements. The inner fender attaches to the cowl and the radiator support, and the distance must be measured to ensure proper fender, hood, bumper, grill, and other parts all align during final assembly. Take the time to measure the distances from a flat point on the cowl (we used the body seam) and the radiator support. We also took a lot of measurements from different locations, just to give us more than one reference point, and we recommend you do the same.
Now that you have the panel resting in its new location and all your measurements taken, use a couple sets of locking pliers to hold it in place. If you are undertaking this job, we will assume you either have a mig welder of your own or have been able to borrow a buddy's. Either way, without it, you can't continue. That's the second specialty tool you'll need.
Now it's time to weld, and the best advice we can give you is to take your time. With the panel in place, begin welding at the center of the hole and work your way to the outside of the circle. Try to keep the weld build-up to a minimum to alleviate the need for a lot of grinding later. If you take your time, you can make the welded spots look relatively close to what a pinch weld looks like. And the subsequent painting will hide your devious secret.
The main reason we needed to replace the inner fender of our Bee, is the battery has leaked acid for years and has eaten away at the metal. Not only that, but a minor fender-bender had placed a few small wrinkles in it. Were it not for the wrinkles, we could have simply patched some metal in the location of the rust hole, smoothed it out, and called it good. | 
Before you even think about removing the inner fender, you need to take a couple of measurements. Take a measurement from a point on the cowl to another point on the radiator support. Another measurement is to measure from the passenger-side inner fender panel to the driver-side inner panel in a couple different locations. This measurement should repeat itself when you install the new panel, but it's better to be safe than sorry. When you install the new inner fender, make sure the measurements are the same before you do any welding. | 
After you have taken all your measurements, you may need to clean off the years of grease and grime to begin locating all the pinch welds. |
After you have located them, a spot-weld cutter is used to cut around the weld, so the panel can be removed. We got ours from Blair Equipment. | 
As you are making your way around the edge of the fender, you will need to remove the master cylinder in order to get to the welds at the back of the panel. | 
If you plan to reuse your brake lines, make sure to carefully remove them as well. |
After you have all the spot welds cut, the panel just lifts right out. | 
After getting the old panel out of the way, it's time to clean up the area where all the welds will be. You will have a lot of small circle pieces of metal sticking up that need removed. These are the center cuts made when cutting the spot welds. Grab a grinder and start cleaning. | 
After you have thoroughly ground all the old spot welds off, it's time to put the replacement panel in place. |
If you are using a panel removed from another car, you already have the welding holes drilled. In our case, we had to drill them. | 
We used a couple of vise-grips to hold the panel in place. You have to make sure the panel rests tight against the surrounding structure so the welding process works correctly. Not only that, but it makes a nicer finished job. After you have the panel held in place with the vise-grips, make sure you have the same measurements as the old panel. | 
Now for the fun part. Take a few moments and practice with the welder on the old inner fender to get the settings where you need them in order to make welds that need the least amount of grinding later. |
Once you're comfortable that you have the welder set how you want it, get to it. | 
There is no way to make a plug-weld even look remotely close to a pinch-weld without some grinding. This will take some time if you are planning to recreate the look of a pinch-weld, but if you take your time, you can do it. | 
After welding, take a final measurement just to be sure. It only took the better part of a day, but now the replaced inner fender gets us one step closer to completing the car. |