I'm trying to put together a couple of "representative" M16 models, namely A1 and A2. Here is what I have so far. The A2 is all Bushmaster with A2 barrel so it's pretty close to real thing. The problem I have is finding an authentic A1 lower, does anyone make those any more. And what's the difference between A1 and A2 lower? I did get the Colt upper that has forward assist but no shell deflector. Anything else I should change to make it close to A1 spec?