Suninmyeyes - the story about the 747 being designed as a military freighter (what became the C5A) is largely a myth. While some of the people who worked the Boeing freighter proposal undoubtedly were involved in the 747 design, the 747 design was basically all new. When Boeing was developing the 747, everyone thought supersonic was the future of trans continental passenger aircraft - which would have soon made the 747 obsolete as a passenger aircraft. So the provisions to make it a freighter were designed in early on (the original 747 concept wasn't a super wide 9 or 10 across fuselage, it was a double decker with two single aisle levels).
A quick question on "progress": there has obviously been great progress in engines, and in electronics. Has there been great progress in aerodynamics since the 747 was designed?
Flightless, there have been advances in aerodynamics (particularly in the use of Computational Fluid Dynamics - CFD). But it's been more gradual and evolutionary rather revolutionary. The most significant change in aerodynamics is the ability to optimize the details, and go 'thicker' with things like wings while keeping the critical Mach down. Thicker wings mean more efficient (i.e. lighter) structure and more room for fuel, actuators, etc.