I decided to hell with my shoulder, and got a 45-70 Marlin XLR. Yesterday was my first day at the range with it. The recoil was less than a 12 ga. using the Hornady LeveRevolution carts. They are only 325 grain bullets, so I can imagine the bigger rounds kick a little more, but nothing to write home about. I figure, if I can't kill it with a 45-70, then I shouldn't be hunting it.
I have the Marlin .450 and you are right you can hunt anything that walks with it. Though I have to shoot it left handed now because I shattered my right wrist right after I got it in an accident. Though a .45/70 is hard to beat for a single gun to do everything so is a .30/06.