You said you have some old GI stuff. I see the M1 Garand guys writing that they clean the wood first (some even do it in their dishwasher), let it dry and use a hot iron over a wet cloth to help raise up some of the dents/gouges in the wood before lightly sanding and refinishing the stock.
I have no idea what the original stocks were finished with but I'm sure you could use an oil finish.
For the metal, some 3n1 oil (or other light oil) with 0000 steel wool added and then lightly rubbed over the metal will remove the surface rust without damaging any remaining bluing.
I bought an old Auto 5 a few years back that was pretty "brown" with surface rust. After the oil/0000 steel wool rub down I was amazed at how much "blue" showed up. It won't remove pits, or put bluing back in a gouge, but it will remove brown looking rust and leave any remaining bluing more visible.