Thanks for those images from the eastern ascent.
The old road infrastructure on that side is equally, if not more, fascinating, and looks like it made for a very narrow, tortuous route through tight tunnels and over rickety bridges. I had noted those sections from my various traverses of the Croix de Fer from/to the Maurienne valley, but was always in climb/descend-as-fast-as-possible-without-stopping mode, so have never actually explored them. I wonder when those old road sections were closed off and replaced?
The helicopter shots from the Tour de France this year zoomed in on that old bridge, prompting me to recall my various trips over the Croix de Fer and the Col du Glandon....and reminding me of the landslide on the west side, that I first heard about in 1988 and have been wondering about the facts of ever since.
As for signs of the old road wiped out by the landslide, well you can see the locations it diverges from the new alignment in the form of gravelly tracks meeting the road (at/near the commencement of hairpin sections built to cross the valley), but they don't stand out much, so one probably wouldn't notice if one wasn't actively looking. I saw on Google Streetview that there is road sign warning of risk of death at another track entrance along the 'new' bit of road!
The old maps make interesting reading, as they always do - I'll take a photo of my 1986 map later on and post it here.