OTOH if you mean the 747-800 then
AFAIK, that doesn't exist, even as a paper study.
OTOOH if you mean the 747-8i (passenger variant) then that does exist -
The 747-800 DOES exist. It is the official designation for the 747-8. A lot of FAA documentation refers to the 747-800, but some refer to the 747-8.