Above the axle tube squashed between the diff and the coil spring. Design it super strong then over build it some more. Put a couple of options in for mounting holes and don't make the mount point too close to the axle tube (in height terms) because it will hit the diff when you flex.Did I say over-build it?
you might want to grind out and reweld the panhard bracket then do a cap weld over the top. At the moment it doesnt give confidence in the weld strength view