re the panhard mounts, i'd brace the axle brackets diagonally from maybe halfway up either out to the axle tube or in to the diff casing. or better still shorten them and lengthen the chassis brackets. so they're about the same length. there's a lot of leverage on those long brackets as they are. if the bar gets too close to the diff by lowering it it can be bent to clear. that only makes bar length changes more awkward but once set that shouldn't ever need altering.
neil.