I will go with 1979 as well. I haven't missed a Tour since 1975 but for some reason I don't remember hearing about HC climbs until a few years after I started tuning in on the BBC. Weren't both the Alpe d'Huez and the Col du Galibier in the race that year? I'm pretty sure the Galibier is HC, but I have been wrong before.
I think van Impe was the winner on one of those hard stages but damned if I can remember if it was Alpe d'Huez or not. It is rough getting old, your memory is the 2nd thing to go downhill.
