Instead of changing an old M14 (sorry) I recommend a brand new one from one of these companies out there which make .308 in AR 15 style.
No thanks. I tried an ArmaLite AR-10A4 and sold it to fund another M14 build.
I have a new lightweight synthetic polymer E2 stock on the way.
It is a drop in stock (no bedding) and it will accept rails if needed.