The design of the 747 fuselage is semi-monocoque. The fuselage is built in sections, which are then placed in a jig so they can then all be joined. The jig is the one of the most expensive parts of the whole process. A jig is designed to ensure that all finished products that come from that jig are identical - within set limits of tolerances. How you could produce two fuselages, from a fuselage jig, with a 75mm variation in length, is something I'd like explained to me in detail. A tolerance limit of 75mm appears to me, to be impossible. I understand that the assembly factory is temperature controlled, so wide temperature variations in the assembly process can be discounted. IMO, the original poster of the 75mm variation is getting his wires crossed, and the 75mm figure is the likely maximum fuselage length variation between major extremes of temperature and extremes of imposed flying forces.
That's what I thought, OT.
I would just like some confirmation of it - or not, as the case may be.