I saw some on a Dakota the other day, pretty slick. I didn't install them, so I can't comment.
As to plumbing the scope, if youre going to be holding over for LR, definately, use a plumb on the reticle, and a level on the action. if youre going to be clicking your comeups, its probably better to level from the turret, since there is usually some misalignment that will throw "level" out of wack between the turret and the reticle. Even Leupold has turned out some that are way off. Their quality controll says the reticle can be of several degrees before they will label it defective.