Well, why do you want to go mag-fed? Is it a style of play you want to try? If so, I'd recommend just getting a T8/8.1, or even just using a 50 round hopper, instead of going to a mag-feed system. It will save you lots of money and give you a similar experience without the hassle of being limited to one style of play.
That being said, I'd check Tacamo's website (they're the ones who make the Alpha Black conversion kit) and checking there.
Christ Krew #17