The stock may work with a standard buttstock adapter, but you need to pick the right pistol grip. The standard M16A2 stock does not allow a good solid grip with the trigger hand. I tried it and it was very uncomfortable. The Magpul PRS just allows you to get the correct grip placement since it doesn't taper down until much farther back than the old A2 stock does.
If you want to use the M16 stock, you need the high buttstock adapter or a different grip that allows the proper pistol grip hand placement.
Tony.