Yes, you'll need the rifle buffer, buffer spring, and buffer tube. Make sure you use an A1 screw to attach the stock to the tube, as an A2 screw is longer and will cause problems.
1. Separate the upper from the lower.
2. Cock the hammer.
3. Depress the buffer retainer and pull the buffer and its spring out.
4. Loosen the castle nut with a telestock wrench.
5. Unscrew the carbine buffer tube, making sure that you do not lose the buffer retainer or the rear takedown pin's spring, as both are spring-loaded.
6. Screw the A1 buffer tube onto the lower receiver, while depressing the buffer retainer to allow the buffer tube to overlap it.
7. Slide the A1 stock onto the buffer tube, making sure that the rear takedown pin's spring goes into the little hole in the right side of the stock. Otherwise it will be pinched between the lower receiver and stock.
8. Place the A1 screw into the top hole of the buttstock and tighten it down.
9. Slide the RIFLE spring and buffer into the buffer tube from the front until it snaps past the buffer retainer. Do NOT use your carbine stock's buffer or spring.
10. Reattach the upper, and go shoot that bad boy.