When you pull the heads, just do as you say, mark and take pictures. Do not scrape the carbon buildup from the heads until you check your engine type, some engines were glass lined, and you'll kill the lining, then it's new heads. May as well lap the valves and plane the heads while in there, and check the cam bearings also. It sounds like a lot, but doing this now will save you a lot of headache, not to mention your new headgaskets, later.