Rebuild questions

[valleyview]

I've got a 2009 Outback with 180,000 miles that was leaking oil from the head gasket so I pulled the engine and am having the heads freshened up/milled before replacing the HGs. The cylinder walls look a little rough with some scoring deep enough to feel with the tip of my finger. If I rebore, I will get new pistons, which is expected but my question is: Do I bore all to the same size and get one size piston or do I need to keep with the A-B setup and purchase "Left" and "Right" oversize pistons? Second question: I have a short block without pistons from a 2004 Outback. Could I purchase pistons for that and install the 2009 heads on it? If so, should I get 2004 pistons or 2009 pistons? Thanks