First off, the .45-70 is not just "a 100 yard yard rifle". Two weeks ago I dumped a buck at 220 yards. Bang Flop. I shoot Hornady LEs, 325 gr., 2050 fps, in a Handi Rifle, out to 300 yards. I'm working to push that to 500. I weigh 150 lbs at 68 years old, with arthritis, and have no recoil problems at all. My 386T .30-30 kicks as hard. In fact I think it kicks a little harder with the straight grip.
As was previously stated, you won't fall apart at 60. Get the .45-70, shoot it and enjoy it, and thoughts of recoil will become a distant memory. I think if you wear good ear protection on the range, your felt recoil will be a lot less. I think what we register as recoil, is in a large part muzzle blast. Hold it in tight, squeeze slowly, let the shot surprise you. It is so simple they even allow wives and daughters to do it.
Good shooting,
Pete