[goofy]

I would wait till the gun comes in and see if it is already drilled and tapped for the x-lock system if it is then you should use them(no reason to add more holes to your receiver) if not use any one you like but have a smith drill and tap unless you are ok to do it yourself.
They have to be centered and lined up so you scope is centered and lined up.
You also might want the rings lapped.
Mike