Flash forward a couple years and I'm finally to the point I can make the repair. After I removed a 1/2" of body filler I discovered a panel is as wavy as the sea, a patch that must have been welded by a bird with the runs, and a grind job (read gouge job) that makes me shutter to even think about. At least the previous owner had good intentions?

I began by cutting out the seam that was welded over with said patch. What I found below was very discouaging. The hole that was caused by the presumed hammer must have been preceeded by what apears to be the B pillar rusting from the inside out. The strange part in all this is that the rest of the car is fairly rust free.

Is it common for Mustangs to rust out at the B pillar?

How does a person go about repairing the sheetmetal and the inner structure?

since i just started my welding carrier it sounds like the guy warped the metel and didnt space out his welds enough.i would cut out all the disfigured metel and start over. I have seen holes form on the passanger side A post up top where it meets the roof line. probably the location of welds. I have also seen rust where the sail panel meets the 1/4 this part is actually filled in with lead and smoothed out. In fact this is the location of rust on my 66.

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88 thunderbird TC 2.3L
Gillis at 18 psi, walbro 255 lph fuel pump, Kirban at 39 psi, 3.73 8.8" rear, rebuilt head, brand new IHI, working on a T3 and FMIC

66 mustang V8 swap baby

Well I've cut it all out. And have the new panel fitted. I now need to address the rust in the structure piece below the sail panel.

To the previous owners credit, it looks like he did at least use some Por15 on the area below the panel to seal the small section he cut out.

I basically have a time elapse of the panel rust. The passenger side was perfect, with no rust. The donor vehicle was in the begining stages, and the drivers side had advanced rust. You can actually see just how it takes place.

Just under the drip rail there is a seam that is filled with seam sealer. When the body cracks at the rear window "V" from engine torque it causes the seams seal to be compromised. Once the seam sealer fails water is pretty much channeled into the seam and the rust forms from the outside further destroying the seam seal. The water then can enter to the inside, sits between the two panels and eventually rusts out the sail panel from the inside out.

So anyone who reads this take a look at the where the sail panel meets the rear side window underneith the drip rail. If you have any rust starting in the "V" take care of it before if migrates below the panel.