Looks like we might have similar ideas.
I´m in Bariloche today heading south to Ushuaia. I was planning to go down RN40 a bit more, possibly cross country to Comodoro Rivadavia, then RN3 to Rio Gallegos, down to Ushuaia.
Then back up the RN40, cross into Chile near Cochrane then up the Carretera Austral to Puerto Montt. Might even go down from Cochrane to Villa O´Higgins to start from the bottom.
I´m on a Transalp (Argentinian Number plates).
Let me know if you fancy meeting up.