There should be plenty of material to work with. You're going to weld the vertical seam and put a fish plate over the top of it. There's two basic designs.
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Reason the fish plate works is that it creates a longer weld area as well as distributing the heat affected zone so that it isn't in a straight line and doesn't create a stress riser.
@WARRIORWELDING or
@mcutler could explain more as to the why. I would say that as long as the fish plate can extend as long as the seam is tall, you'll be just fine to patch it back together. Hopefully I provided a half decent explanation.