CC, yes it's the elevation. I'm not sure on the action, bought it about 4-5 years ago.
One of the problems generated by the trend to using high magnification scopes is the higher the magnification, the less adjustment in the scope. You mentioned that you had Talley rings and bases. That is who I would contact before launching into an expensive custom project. You may need a base (front or rear) that is a little thicker/thinner than normal. Normally, I would suggest a shim inside the ring, but with the vertical split Talley rings, that will not work. I have had no trouble with the Talley rings and bases on my .358 Win. pistol. They make a fine product, and I have found them to be very helpful at the SHOT Show. Give them a try.
Another alternative, if the Talley route does not work, would be to contact Weatherby. Some years ago, one of the big name gun makers released a batch of rifles, in which the machining was off slightly. This caused an unbelievable amount of problems with scope mounting, I would be surprised if this was the case with a Mark V, but you never know.