Well our B757 (freighter built by Boeing, not converted) has a max payload of 39 tons and change (15 pallets). With fuel on top of that (about 24 tons), weŽll go about 5,5 hrs, landing with about 4 tons.
Not to far from the DC-8-55F if I recall correctly, same number of pallets, OEW about 140k lbs(if memory serves,many a loadsheed handwritten...) payload 100k lbs (45 tons) and fuel 85k for a MTOW of 325k lbs. That would have meant a range of about 5,5 hrs burning about 13,500
pr. hr and landing with 10,000 lbs.
Numbers are not too different really.
