I have fished Hungry Horse and the Flathead above, also packed in 25 miles all along the river for elk hunting. I would never elk hunt that area again but I would damn sure enjoy what your talking about doing the river is stunning through there and the fishing is great.
Here is link to one outfitter that packs in and floats out.
https://www.montanaangler.com/montana-fly-fishing-trips/bob-marshall-south-fork-flathead-float-fishingBears. I would not worry about the bears one bit. Problems with them are way over dramatized.
There is an outfit that has cabins & horses very close to the meadow creek trailhead but I can't recall the name.
I will update with some pics of the river you would be floating on if doing the south fork.
“You can resolve to live your life with integrity. Let your credo be this: Let the lie come into the world, let it even triumph. But not through me.”
- Alexander Solzhenitsyn