Shotgun, Quite often I spend $300 to repair and refurb what ends up being a $200 rifle. Tis the nature of this hobby. But if I may offer a suggestion to you.
Go Google 'Springfield Sporters' and try Googling 'gun parts, west hurley'. Go poke around on these two websites and you will find exploded diagrams of your rifle. You will be able to see what parts you have missing from your rifle and what you will need to put it back to mil spec. Once you know what you need, you can go on the hunt for parts.
It can be expensive if you go the easy route and order them up. If you are not in a hurry there is an alternative. Keep your eyes open for the parts, and only buy them when you can get them for a good deal. Watch the on line auctions and network with other collectors. Most people into these rifles are usualy willing to horse trade for some of the extra parts that they always have stashed. ;
So if you are not in a hurry, it can be done relatively cheap.