I travel to SYD a fair bit. I have had 50 minute layovers. If you arrive into the E gates you need to hustle to the G gates, but more often than not if there has been delays on the earlier flights into SFO they will put me on the delayed earlier flight.

Also, the advantage of SYD flights is there is a flight for SYD out of LAX so if it looks like you will misconduct SFO-SYD they can probably reroute you to LAX-SYD. The arrival of both flights into SYD is quite close on arrival times.

Enjoy your trip! It will be cold. I will be there in July. Brrr