Is this possible? Legal? if so how?

Quoted: Is this possible? YES Legal? It depends.  Do you have enough US made parts to get around 922(r)? if so how?Contact a smith, and beware, because it generally involves machining on your bolt and/or receiver.  Rumor has it that an AK mag conversion that wasn't done at the factory, usually breaks and renders your gun useless sooner than it should.

The bottom line, if you want something that takes AK magazines, IMHO you should buy an AK.  Although I don't like them, the Romanian variants are fairly inexpensive compared to a NIB or LNIB original Norinco that was factory modified to take AK mags.  A local dealer has a new Norinco that takes AK mags for $450 whereas I can purchase Romanian AKs in the $325 to $385 range until the cows come home.  

If you want to spend a little more, look at the ROBINSON ARMAMENT VEPRs that take AK mags.  Although I have not shot their VEPR, I have heard that it is very accurate compared to normal AKs.