I saw a couple of rifles some time ago that were standard half stock rigs that had the forearm extended to make them into full stocks.
One of them incorporated a brass spacer at an angle between the original stock and the new addition to the forearm. Another had an ebony tip added and shaped somewhat like a Sav 99 EG. They were nicely done and professional looking.
Depending on what you have and what you hope to end up with regarding barrel length, you may need to shorten the barrel and reinstall the front sight.
Lots of options for a open mind.....