With the goal of doing well as a GC in an early stage race, IMO, you will need some time trial work in the time trial position. I do not care if you own a TT bike or not. The time trial is where you can differentiate yourself from the field in the GC category unless there is a hilly long road race that will break up the peloton. Sooooooo..... without studying your specific plan, I suggest making sure you get some 2x20 z4 intervals on flat to rolling terrain and a practice time trial or two before the stage races. Good luck.
Edit: If the 2x20 z4s are too tough then do 2-4 x10 minute z4s.