Here's a shot of the area behind the half-ass patch on the cowl side panel. I cut out the weak metal and made this patch in a few layers to mimic the stock flanges so that it looks correct. You can't see this area with the fender on, but I would know if it was half-ass...
Before:
After:
I also seam welded the toe panel (floor pan to firewall piece) since I didn't think it was installed with as many tacks as I wanted and it's somewhat structural in the unibody. Much more rigid. I also found that the forward area of the cowl panel was attached poorly so I cut it back, cleaned everything and folded it over to make a smooth transition. Looks stock and is much stronger than the original design. Again, you can't see these areas, but those details are what makes a good build.
I did decide that the cowl panel itself needs replaced. This is a common issue on early Mustangs. It's only a couple hundred dollars but is a fair amount of work. I will order it as well as torque boxes (reinforcements between the frame and rockers/floorboards) for installation soon. The 65-66 cars didn't have torque boxes, which hurt rigidity, but they can be added. After that I should have a good body all around and then get started on some reinforcements and modifications.
