A savage 340 is a great little rifle. It sounds like you are planning on building a custom rifle
using your grandpas rifle, but when you are finished you will have a new rifle with grandpa's action. Now to answer your questions. A custom stock can be built for just about anything,for a price. Good walnut stocks can cost thousands, Composite stocks can cost almost as much. I dont know of any semi-custom stock builders inleting for the 340, You could check with Richards Microfit stocks, if you can reach them. We can fit a barrel to almost any action, if it is safe to chamber the cartridge in that action. You should probably plan on spending 250-300 on the barrel plus another 150 minimum on the barrel fitting. I haven't even said anything about all those other small things that add up so fast, like blueing, trigger, scope mount ect. I hope I am not discouraging you, but I see people every week with a dream and little idea of the costs involved. May I propose another solution? The 222 is a fantastic cartridge, how about keeping the factory barrel, refinishing the factory stock ( a great project for a do it yourselfer ) , and having the metal refinished. You would end up with a great little rifle. What ever you choose good luck and good hunting.