ok brave choice !
After you climb the Izoard mountain pass (2360 meters !) you are not in Italy yet, follow the D902 road after the climb then turn left into the D947 road, the right into the D5 road and finally left again into the D205 until the french italian border, which is the
Colle Dell Agnello (2738 meters !)
p.s. Grenoble to Briançon is a continous raising false flat, during the first 80 kilometers (from 107 kilometers total), going from 200 meters to 2000 meters (Col du Lauteret)
Arriving to Briançon, good place for a rest day, you will know better if you can challenge the Izoard route. If you decide not to, no problem because you have alternatives, at least two, one going around the Izoard in direction to Embrun and the other by Sestriere or Oulx in direction to Turin.
remember that these roads (the ones with mountain passes) are not open year round, because of snow,