Finally, all closed up and just a bit of grinding before it's time to lay down a few coats of Bloxide. | 
To recreate the doubler plate I start working a piece of 18 gauge over a t-dolley, which makes it easy to hammer in a couple of bends with just the right radius. | 
Remember, there is no "right" way to create the geometry you need--use every tool at your disposal. This turned out to be so easy it felt like cheating: I sandwiched the part between two chunks of aluminum and cranked it down in the vise until I had what I needed. |
After creating the bend, I need to put a radius into the part such that it matched the curve of the wheelhouse. After a bit of head scratching I noticed a power steering pump pulley from an LT1 would give me just the shape I needed. It's a little barnyard, but hey, I never said I was Chip Foose. | 
Before welding the double plate in place, I laid down several thin coats of the Bloxide weldable primer and then a bead of seam sealer, also sourced from Eastwood. | 
The replacement doubler plates get a coat of Bloxide and holes punched for plug welds. Notice how I copied the radii and geometry from the original parts. These could have been a little cleaner looking, but once welded, seam sealed, and painted the repair shouldn't draw attention to itself and is structurally sound. |
Welding Bloxide-coated parts requires a bit more voltage, so experiment before you get started. Again the part isn't an exact fit, but it's close enough that I can massage it into place with a hammer and a piece of brass. | 
I saved my worst work for last. This is the corner of the car I started this project and the learning curve on. Before I started I had practically zero experience welding or repairing sheet metal, but was still able to create a structurally sound repair, albeit not the prettiest. The upside to the hidden damage on these cars is that it's a great place to learn the basics because you will cover it up when you're done. | 
The angle grinder reveals the heavily damaged underlying structure. Be aware of the thicker piece of sheetmetal now hanging out in space, which is the main support for the door hinges. After scraping up the tar-like seam sealer and cleaning it up with mineral spirits, the floor pan looks deceptively solid. |