I would first measure what geometry you have at the moment, that will tell you where to make any slot and in what direction.
The ford adjustable arms were just the std arms with the ends cut off and a tube welded on in which sat a heavy duty rod end, and a nut either side of the tube bit securing the rod end in place, thus when the rod end was moved raletive to the arm you have adjustable camber and toe.
tabetha