Rocker meets cab corner??

[muddpile]

Where the rocker meets the cab corner, there is a vertical seam. What do I do with it? Do I weld it up and then filler it, or do I just put some seam sealer in it? I haven't done anything with it yet, as I have no idea what to do there, and when I started that whole area was rusted away, so no clues from that.

Also, where do I use bondo vs. seam sealer. For example, on the back and side of the cab where I welded the new cab corners in, do I use filler to smooth that before I paint it, or seam sealer? I assume filler, but I'm not sure, so I thought I'd ask. Thanks!