I installed a Criterion barrel in my dad's Garand... and they are excellent.  I haven't installed one on a Krag, but I do understand that they come indexed and reamed (head space is set to the rim, so head spacing is not critical).  The location for the front sight is milled, and the holes are drilled for the rear sight (although I have heard that they are not drilled and tapped to the thread pitch of the original Krag screws).  They DO come "In The White", which means they have no finish.  You will have to have the front sight post installed.