I would clean the frame rail to bare metal passed the OEM Galz.coating.Use a small grinder and bevel the crack to the inside of the frame rail.I would use a tig welder to control the heat in the weld zone.Then metal finish the weld smooth.Trying not to remove any of the frame rail material.Fab a small diamond shaped gusset(3in.tall x4.5 long) for the outside of the frame.Then I fab surport gusset the shape of the frame from the lower bracket to upper on both sides of the the frame.This should spread out the load from the upper link's thur the side of the iner frame back to the shock cross tube.Todd good luck.If you were closer I could help you out.
Scott M.