Gosh Duke,
The problem is, that you say you want a rifle that is both a good white-tail gun, and a good grizzly gun. They are apples and oranges. One animal weighs 150 pounds, can be killed easily at long ranges, and is not dangerous. The other can weigh 800 to 1,000 pounds, is hard to kill at long range, and can kill you.
With all due respect to all of my friends on this board, there is no single gun that is going to be great at both of these. So, why are you trying to "compress" these two extremes into one firearm? Rifles are not that expensive, especially if you buy them in used VG+ condition. So, do right by the game, and buy two.
Now, if for some reason you just must have these capabilities in one rifle, then the .45-70, or a .35 Whelen, would be the round. BUT, you are limiting both your grizzly shooting and white-tail shooting to approximately 225 yards. Are you willing to do that?
Some folks have mentioned the .300 WSM, which is a great round, but I feel that it is too light (not a fat enough caliber) for grizzly.
The .325 Ruger will be dead in 10 years. If you go in that direction, then get a .338 Magnum, and hand-load down some cartridges for white-tail. The .338 is a proven performer, especially on grizzly, and is here to stay.
Just my thoughts,
Good luck,
Mannyrock