I would have said the 757, due to its range and capacity, but now i would probably say the 777-200LR, or even the new 7E7

That’s quite a jump going from the 757 to the 777/7E7.

There’s no way an airline is going to suceed trying to operate a narrowbody across the Pacific. Besides, whatever happens to UA’s and DJ’s codshare agreement? In UA’s Hemispheres magazine, they have DJ as a codeshare partner in Australia. However, I never see any DJ routes when checking UA’s schedules or making reservations.