Regarding the range of the B767-300ER, have frequently flown Manila-Bahrain with a full load, into a constant headwind, plenty of fuel to spare.
Example I used was an example of an actual flight, Europe to U.S., against the polar jet stream. Looked at yesterday's data and it would have been able to take a full load, at max gross takeoff weight, and complete the flight. One flight was restricted by approx. 40 passengers while another flight was able to complete the segment at MTOW w/full load.
So 4,600 nm with a full load, against the winter polar jet stream, is getting close to the operational effective range.
Manila - Bahrain, with the sub-tropical jet, on average has lower headwinds.