I hunted Alaska for most of the 27 Falls I lived there with Contenders. I used 14"/15" barrels mostly, but I had good success with 10" barrels too. While is doesn't really answer your question, I used short .30 Herrett, .25-35 and .45 Colt barrels to good effect on deer and caribou.
I'd recommend a .44 Mag or .445 SuperMag in the 10" barrel. The .45-70 loses too much power in the short barrel (200-300 fps) and becomes very unpleasant to shoot (it ain't a peach in a 14" barrel either!). Plus it just isn't 'needed' for most Alaskan game (although I've used it extensivley). The result is performance about on par with the .445 SuperMag anyway. This latter is not a pussycat with full power loads, but it can be loaded down for deer, etc. With a 200+ fps advantage over the .44 Mag, it is a good choice.
Don't consider using a Contender as a grizzly hunting arm, although as defense it 'works' I guess. I've faced down several charging bears with a Contender, and it wasn't a fun experience - at the time. :roll: