I don't know if the weight of the passengers would be enough to invalidate the cargo capacity, also depends on the stage length, outside temp, elevation of the runway etc. Having a large cargo bay definitely makes Airbus a better bet than the 767 - incredible arrogance of Boeing to build a widebody trunk liner which can't take LD3s. And the rear cabin isn't cramped, in fact cos it's slightly rising at the back you can see a long way forward, slightly over the top of the rows in front, making it feel less claustrophobic. And when an airliner is in the cruise, there is a slight nose-up deck angle which means that the rear cabin of an Airbus is actually parallel to the ground (as opposed to slightly 'uphill').
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz