I think mkeller is onto something; i.e. "bike du jour" at Raleigh. The 75 or 76 GS that I acquired used (recently) had quite the mixed bag of period correct but non-catalogue components; mostly upgrades from what is in the catalogue. Since there's little rhyme or reason for the suite of components that differ from the catalogue, it seems plausible at least that these were not implemented by the original owner, but rather just resulted from the factory consuming what they had on hand when outfitting the bike. Or maybe the original owner just had a whimsical streak. That said, I should add that all the components in question are not at odds with the GS's purpose and market position:
FD: Campy NR
RD: Crane GS
Shifters: Campy NR
Stem: SR
Bars: SR World Randonneur
Go figure.