The pillar is made of an inner and outer layer and the drip rail is spot welded to the outer layer. Mine rusted there, and where the weatherstrip touches, like you said. I cut the roof off a wrecked runner years ago to do the repair myself but:

1) I never got around to it
2) I don't have the bility to paint it properly and
3) My welding is more about function than looks

So I asked Corey to do it with the body swap.

Here is a picture of what I cut off the wrecked truck. Even though it looks 'clean', there is rust behind the drip rail, which is why they were cut off the A-pillars.