Basically it all depends on gross weight and altitude. Basic operating weight of the average cargo 747-200 is about 350,000#, add about 45,000# of fuel for just goofing around in the pattern and that gives you a total of 395,000# takeoff weight for a minimum operating conditions. With a max gross structural takeoff weight of 833000# that gives you a possible increase of 2.1 times a minimum operating weight of 390000#. Now you also have a maximum landing weight of 630000# which still represents 1.6 times more weight than your goofing off minimum takeoff weight. So in short your clean manuevering stall speed is going to vary an awful lot just on gross weight alone. There are many other variables involved as well, and we have not even got into the discussion on minimum flap manuevering speeds as well. Pretty much all these parameters as calculated prior to takeoff and landing. There are on the old jurrasic jets little plastic "bugs" that are positioned around the airspeed indicator to note the different speeds.
The 747 is definitely not your father's Cherokee!
Good Luck & Have Fun!