The best that I can do is a Manila - Sydney sector on the B707-338 which was 9 hours 30 minutes.
Also a Saigon - Sydney sector on VH - EBP (B707 - 338) on 4th March, 1970 which was 10 hours 03 minutes.
I have passed the word around so someone might be able to come up with those specific sectors.
Regards, Norman Wells