I want to use the tax credits available and replace my reliable Trane air conditioners(downstairs and upstaris units) installed in 1984. They use R-12. From googling it looks like R-22 is not available in 2010 on new systems and this leaves R-410A(Puron). From reading it looks like the supply lines are going to need to be replaced for R-410A and the one running to the upstairs unit goes into the basement up interior walls all the way to the attic. And I do not want to run the line on the outside of the house to the attic. The downstairs will be ok since everything is in the basement.
Are there any other options? Like a different refrigerant, etc. I live in North Carolina so summer heat is high.