To me this sounds like the job for a 30-06 or 300win mag. Others will work but I like these based on what you wrote.
Yes I would use the same gun for inland griz. The size you state for this bear at 550+ lbs is in the same ball park LBS as an inland griz.
Having said all of this, if I had a 338 mag or 340 weatherby, I might, and I emphasis might, take this gun. I would have to factor in the the added weight of the bigger rifle into the overall equation since this is a spot and stalk hunt. The 30-06 or 300mag are more than capable med size bear killers even at the range stated.
Did I pass the Test ?