That bracket with MOOG cast into it is likely aftermarket. Good thing that ugly patch (pics 4 and 5) is at the rear of the frame. If it was forward of the axle, I'd be inclined to fishplate it on the inside for structural integrity. Not as critical at the rear. Welding on a frame, especially the flanges is generally a no-no, and will weaken it.
I agree with Otto, that POR15 is probably overkill, especially if you blast it.
On the spring pins, DO NOT use an air hammer. That'll just mushroom the ends. Use a ball joint press. The pins may thread in like the 1/2 ton trucks, although the bushings are pressed into the spring eyes.
