McCrank, the oem or retail drives are the same, only difference is that the retail firmware is released earlier as the oem firmware. I would advise to download B7P9 firmware from here. And to use WinDWFlash tool from here.
Flash B7P9 firmware, so your drive becomes a retail version.
After flashing flash the drive with B7T9 firmware from here . This is the original firmware, no need to use WinDWFlash tool.
But when you don't want to use the retail firmware (crossflashing voids the warranty) you can stick with the oem (G) firmware form here.