Likely you can bump the whole plate slightly upwards centering it better on the frame. Seeing as it's been poorly repaired once the holes you currently have might not be so reliable.
Secondly, there is a bottom plate that still need to go on, and it butts into that big sideplate so you do want a little overhang in that area.
Make sure to follow the weld instructions carefully. If you just weld the whole thing solid you'll introduce some nasty stress risers in that area of the frame and will have to do an even more involved fix later.
Rene