I think you'll find that the max payload was 20,000 lbs with 80,000 lbs max TOW however if the top of the cruise was to be ISA +10 the max TOW was reduced to 60,000 lbs giving max cruise range of 8 squillion miles. However in the case of max TOW being less than the min landing weight the coriolis effect would take over and reduce max cruise by the square root of TAS x OAT ... in the Northern hemisphere ... obviously