I ordered an insert from MCA sports for another rifle, so I'll let you know. I got one of those sketchy 1916 Mausers that were re-barreled in .308 and I am converting it to shoot 7.62x39.You ever used one? From what I've read the x45 mags don't feed x39 reliably, and the inserts aren't very reliable either.
With regard to mags, you would probably best be served getting the mags for x39. They are about $100 each though... would be cool if you could convert it to take AK mags