Rely on the 737 but hope for the airbus 330 is my motto with both QF and VA.
Both have more 737s flying than airbuses, and if you have a look at the weekend schedule, trans Aust, its more so the 737 that will do your flight.
I don't have high hopes, one time, I booked to sit in QF J from MEL - SYD, they swapped my planned plane from the airbus 330 to 737 at least 3 times, and 3 times, I had to sit and wait at least 45 mins to get changed timetable so I could try the airbus 330 J.
They can change a plane overnight, so even if you checked in OLCI with showing an airbus 330, you could get to the airport and get a 737!
The last 767 flight, I was booked in Y, first flight at 6am SYD - MEL, (before it was retired), I had done OLCI and had a BP on the ipod, was staying at the ibis Budget SYDd airport, got to T3, was at the right gate and saw to my utter dismay, a lowly 737 sitting at the gate my 767 was to depart from.
Had asked what would happen on here if it happened, and it did happen.
Members on here said to ask at the QP for a change in time of departure of flight, asked in QP, and the lounge goddess swapped me to the 7.30am flight, which was a 767.
The time I met JessicamTam, a mod on here, also QF changed that 767 last flight to 737.
Unless QF brings more airbus 330s in operation, or put more boeing 787s onto domestic operations, the 737 will take precedence.