DL283 / 284 (ATL - LAX) should be the natural extension of the LAX - SYD route that operates the same plane.
I've taken DL283 once late October. Called in to use one of my RUCs, waitlisted and got cleared 1 day prior to departure. There was only 1 seat left with 50+ people on the upgrade WL.
The service onboard was the standard domestic F class service: thin blanket, welcome drink, F class style food was served, and that's it. But the D1 suite was really comfortable that I managed to add two hours of sleep on the way.