You need a forend, a rear handguard, a front handguard, and ideally a matching butt. Then, a few metal bits:
- rear handguard retaining ring
- middle band, screw and swivel
- front band and screw
- rear swivel and screws (if missing from the sporterized donnor)
- Butt plate and screws (if missing too)
- You may need a new metal bushing under the front of the trigger guard, through which the king screw goes, if the one you have is too short for the new forend.
I think that's it?