The barrett has a 27 moa rail so adding that model Spuhr will give you a 57moa total and you might not be able to zero at the distance you want. The barrett rings, badger rings or american rifle co rings would work well.
There is a thread on here about vertical split rings and how they can cause issues. The American Rifle Co rings are not true split rings and are gtg. I'd skip the larue mount.