Stainless or Aluminum will work equally well; your intake is cast Aluminum. 2003-2007 use the same kits. I just put the Sinister Diesel kit on my 2005. I don't have a tuner so, I cleaned and reinstalled the EGR valve to prevent check engine codes. There are no longer any exhaust gases flowing into the intake, so the EGR valve isn't controlling anything.
When you see all the soot in your intake manifold and imagine that stuff going into your combustion chambers, you'll be glad you are putting an end to it. EGR systems are just crazy to use on a diesel.