These parts should allow you to convert a airsoft AK by UK Arms into a passible Fallout 3 "Chinese" Assault Rifle. The weapon in the game is a cross between an AK and a Soviet squad automatic called an 'RPD'
Print out the "Gas-Block" and "Front_sight" then glue them together. The gas-block/sight assembly simply slips over the existing gas tube.
Remove the existing fore-grips from the airsoft (they should snap off with a little prying from a flat-head screw driver). The "filler block" slides on (see pictures) and is held in place by the grips - you will need four machine screws and nuts to clamp the fore-grips to airsoft body.
The shoulder-stock is up to you (I did it with CPVC, some wooden blocks, and foam floor mat (for the recoil pad)