My son, who has (3) AR-15's in various configurations, has offered to build me a Cali approved AR. He has a legal lower and asked me what I wanted for the upper. I need some advice on who has the best mail order prices, and which upper you prefer. I am left handed, so this will have to be on my list, but what is the best upper for the price. This will be for our upcoming zombie attack, that I will sling up, next to my Glocks in my back pockets. Thanks for your help!