Recoil of the .45/70 ranges from pretty mild (from the standard factory load with 405-grain bullet at 1330 FPS) to downright brutal (a 400-+ grain bullet at 1800-2000 FPS from the custom ammo makers). The question is not "is the recoil manageable?" but "can I handle the recoil of the .45/70 load I intend to use?" How much recoil can you tolerate?
That is very true. I have a Marlin .450 which is basically a hot loaded .45/70 and the recoil is definitely stout. Depending on the person some people can shoot it with no problem and other people refuse to shoot it after the first time.