Which unlocked iphone 5c/5s can I buy in the United States for use BOTH in USA and in South KOREA?

I would like to buy an unlocked iphone 5c or 5s in the United States and use it both in USA and in South Korea while traveling (both phone and LTE data) by swapping nano-SIMs (using USA carrier nano-SIM while in US and using Korean carrier nano-SIM while in Korea). Apple's LTE information website says i need model A1529 (5c) or A1530 (5s) for use in Korea. However, A1529 or A1530 are not sold in the United States. Can I just buy unlocked T-mobile iphone 5c/5s from USA and use it both in USA and in Korea by just changing the nano-SIM? Is there something special in A1529 or A1530 models that only they can be used in Korea?

Thanks in advance.