Australian Ghia and Rs 2litre struts are the same i believe. (1.3, 1.6 etc had a smaller diameter shock).
It was only the UK ones which varied.
Lowering depends on a few things, do you have standard or RS mk1 guards? What size wheel/tyre etc? 1.5"-2" is usually fine.
I saw some King springs on ebay recently. $135. Seems alright.