R1 is 144mm wide outside of fan clips. That is 72mm center CPU toward PCIe. GA-X00M measures 74mm center CPU to near side of PC|e socket. This is done using GA official top view of motherboard and scaling maeasurements bases on 2011 80mm mount spacing. I've done this a lot over the years and never been more than 2mm off, so it should fit. Worst case, insulate the fan clips.