You need to check on mags, I think the ones people say work best are called frankenmags, because they mate the top of an ar mag to the bottom of an ak mag. It gives you the proper curved shape that works best with the round.
Unless you have a cheap supply of 7.62x39, you might want to consider one in 5.45x39 to take advantage of the cheap supply of ammo. It can be had for $150 a thousand right now. I was planning on buying one, but bought an ak-74 instead, new with three mags, bayonet, for $400 out the door, and it has the rail on the receiver to mount a scope.