you could carry something like 1200 people legally* in a 747 freighter.
* In terms of weight, not seats!
How many lower deck seats?
It is lowish - 163 cm high containers go there, so floor to ceiling is about 170 cm. But people enjoy sitting in Learjets, 150 cm floor to ceiling. So, what would a 747 be like with no cargo holds and seats installed throughout lower deck?