Hi TTD,
I believe the Pod Nod was done on a few of the classics as part of the Ultra Long Haul programme, when CX stretched the range of selected 747-200's ( and one -300) with extra tankage and upgraded engines to do HGK-LGW/YVR
Also the 747 was designed when the price of fuel was significantly lower. As the price of oil went through the roof in the 1970's, the fuel costs dictated a lower cruise speed for economy.
Lower cruise speed means higher angle of attack and body angle , which leads to the design engine thrust line being a little out. Hence the mod.
Fly safe.
