The lower ball joints changed because they were actually weak, the later ones were a strength improvement. And that wasn't just a 73+ thing, the ball joints actually changed well before that and even for the 10" drum spindles.
I don't know a lot about them as none of my cars had them, but I do know some folks won't run them because of the strength issue.
I haven't converted any of my cars to rack and pinion, and I think my lack of knowledge on the Aussie cars is going to be a pretty limiting factor on any advice on one. My wheelhouse is really the '71 up cars, and left hand drive. ;)
