I just got through building a lefty AR for my wife based on a stag upper. Great all around but some things I have learned in the process regarding lefty's and AR's might be helpful to you. So long as whatever, normal, upper you get has the shell deflector on it then it shouldn't be too big of a deal for most people. My wife even admitted that the amount of gasses that travel out of my right-handed AR don't really bother her. Also, if you have normal size fingers/hands an ambi mag and bolt release are not needed really either as both are fairly easy to reach while operating the weapon from the left hand. What has been invaluable to her has been a left handed extended charging handle(Badger Ordanance) and ambi selector(stag arms, dpms, troy ind., etc). If you want to mix and match there will be opinions all over the place on what type of upper and lower to go with but if you want a complete rifle that doesn't break the bank then you're probably looking at dpms or S&W. It is VERY easy to fly right past the $700-800 limit though. IF you find yourself in that position then I would suggest Stag(with the upgraded M4 options), Spikes, Wyndham(the old Bushmaster crew), or my personal fave Armalite. A couple hundred more past that and you are in the Colt arena. Just my $.02
