It will fit on an A2, as the reciever extensions are the same, but there is a spacer that fits on the end to allow for the longer A2 stock, and also has a longer screw. DO NOT USE AN A2 SCREW!! A2 screws are almost 1" where as A1 screws are like .59" and the screw will protrude into the reciever extension, and destroy the urethane bumper on the back of the buffer, as well as affect function of the rifle.
There is a really nice A1 stock, with a mottled pistol grip on gunbroker, with $20 buy it now. If you buy that set, I'll swap you that VFG that I have for the A1 grip.
New production A1 stocks are available in colors from Cav Arms, if that matters. The nontrapdoor buttstocks are technically M16 stocks. The trapdoor for cleaning kits was part of the A1 series of improvements.
I may have some M16 &/or A1 stocks and probably a few sets of triangular foreends and old style pistol grips in storage. If you can't get hooked up, let me know and I'll see what I've got.