In the cases of -436, -438 and 4B5, the 36, 38 and B5 are Boeing codes designating the customer for whom the plane was originally built. These designations remain with the planes for their entire lifespan, even if they are sold to other airlines. As such, they are all 747-400s and there is no difference to them save, perhaps, livery and engines. Some examples - UAL is 22, American is 23, Eastern was 25, Japan Airlines is 46.
Note, though, that since the designation is for the life of the plane, a given airline may easily have 747-400s (or any other Boeing type) with individuals bearing a variety of codes due to mergers, used purchases and so on.
There is a listing of the famous Boeing airlines codes somewhere on the Internet. Perhaps one of our friends could remind us all.