168 or even a 180, if it were me. Better BC's and longer barrel life...if that matters to you. If not, the 140's will be screaming and will def. do the job on all whitetail.
I agree with the 168 or 180 berger or even the 175 SMK, especially if it has the loooong factory throat. The 175 SMK will make the jump to the rifling better. I have heard good reports of the 175 on red deer out to 750 odd yards.
yeah i would say at least 168's that things so far over bore take advantage where you can. I would shoot the heaviest bullet my twist rate allowed.... theres no reason not to.
How far are you considering long range? The 140 will flat out fly out of a RUM. It will work fine on a whitetail. I shoot a 140 out of my 7MM Mag at 3400 fps and it gives up very little to the 168 at 3000 fps, mostly windage. A perfect combination of speed and BC. Run the numbers on a ballistic program and you will see. As far as performance the Berger acts like a grenade and kills very well. I also use a 180 VLD in my 7MM STW for elk. It shot better than the 168.