It looks to be a nice sporter. You might just want to leave it as is The price of the stock (the original companies have been out of business for 67 years) and a replacement bolt would probably be almost as much as you would spend on an original rifle. Not to mention that unlike American rifles where "stocks is stocks and bolts is bolts", japanese Type 99 rifles were made by eight different arsenals. As the war progressed, raw materials became scarce, courtesy of the U.S. Navy and U.S. Army Air Corps. The original design was changed to save material and speed up production. So to make your rifle correct, you would have to match arsenal and series. Finding the correct parts would be a challenge, and the bolt would still be mismatched. In Econ 101, I think they called it the "point of diminishing returns". :>)
Dean (the other one)
OFC-Orange Co. Ca Chapter