I wasn't trying to convince anybody on the 45-70...just stating my experience. I have put a few blackies down. Most of them with a .308, but the 45-70 is handier (the rifle is shorter, lighter and a lever action), and more forgiving of bad shot angles (not to be confused with bad shots).
336A,
You are blowing the recoil if the 45-70 with 300 grain bullets way out of proportion...its not that bad, even with hot loads. Now when you get to 400 grain bullets at nearly 1,900 fps it does have considerable recoil.
And...with factory loads the 45-70 is a pussy cat, with no more recoil than a 30-06...maybe not as much. These factory loads will anchor any black bear within 200 yards, but the trajectory is a bit arched. By loading the 300 grain bullets at 2,200 fps...the 45-70 is a genuine 200 yard round without the punishing recoil.
And last but not least...the 30-30, 35 Rem., 375 Win., 444 Marlin will also do the job, and quite well.
To the OP,
Get a Marlin 336 in 35 Rem...the middle ground. For black bear you CANNOT beat a lever action.