I would think nothing smaller than a .460 weatherby would be in order!! God I love posts like this!!!!
Why not do the sensable thing and ask your guide, you just might be suprised at what he would say...ya just don't need no big gun to shoot a tree'd bear at 30/40 feet!
Unless yer just lookin fer an excuse to buy a new gun and feel you need to justify the purchase!!!
I personally would use the lightest rifle I could find in a .223/.243 class!!!