I think Farrell has the chance to go high risk high reward in this final test...
Skelton and Valetini were clearly not fit, Lions out lasted the Ausies.
I'd go with:
Genge Sheehan Furlong
Itoje Beirne
VDF Conan Morgan
JGP Russell
Aki Jones
Lowe Kinghorn VDM
I know what your thinking, scrum was superb with Porter, but I genuinely think Dkeltons size causes scrum issues for Aus.
Beirne from 6 to lock is risky, but VDF can help in the lineout, as can Conan.
I'd prefer TUI and Ringrose, and if that was possible id go for it, but neither seem good, and Aki Jones have proven strong enough in 2 tests now.
Id keep Lowe, for his weaknesses he creates in the red zone, and VDM finishes. Keenan Lowe and Freeman look poor as a unit, Keenan and Freeman have been good though, but I would want to put the hammer down.