OK, reporting back for anyone playing at home: the arms fit up totally fine, a direct swap from factory arms - thank you SAV-84C for advice.

The only odd thing (given the direct swap with no modifications) was that after the car was lowered, we found the wheels pushed out a little and were running crazy camber as a result. After an alignment, it's all running perfectly now.

Your new LCA looks great, and I have a similar problem for my front LCA as well, but my Subaru dealer quoted me $770 each for the genuine front LCA $1540 a pair plus labor

Yeah mate, new from the dealer would be a killer. Grab’em second hand from a wrecker.

Good idea, picked up a pair of good conditon LCA from the wrecker yesterday and just put it on by myself today, problem solved However, I plan to change the new OEM bushes after 1yr for peace of my mind.