Ilsac GF4 is designed for fuel economy and the oil which meets the specification is normally very thin (i.e. 0w20 max 5W30). If you have to use a ACEA equivalent, I would suggest you to go for ACEA A1/B1 compliance oil which is also designed for fuel economy.
It's amazing how the oil spec for any engine can very between countries.
I'm in the US, When I use to work at the Toyota dealer we used 5w30 in the Camry's, and Highlanders, that were equipped with the 2AZ-FE.
But if your engine specs 20w50 in Australia, you should be fine with a A3/B3 oil like M1 0w40, or GC 0w30 if available.
Even a 15w40, or 15w50 would probably be ok.
It seems that you could use almost anything if it specs
5w30 (I think alot of them were back spec'd to 5w20 for CAFE reasons) in one country and 20w50 in another.