All my 45 cal's(458 American, 458 WM, 45-70, -90, -100, -110, and -120) like the Oregon Trails TRUESHOT 430gr GC with AA2700, AA2460, Varget, H4895 variously. Accuracy depends on the sights...scoped run ~1 - 1 1/2, aperature and my old eyes run 2" for 3 shots. This is as good as jacketed bullet of similar weight...400 to 450 gr.
The TRUESHOT bullets are the most uniform cast lead bullets I have ever shot, in weight, OD, length and ogive points, equal to or better than many jacketed 45 cal bullets, and penetration is on par with the jacketed brethren.
The 430 gr is a very good compromise between bullet weight and recoil. Velocities run ~2000fs to ~2600fs depending on case size. The 45-90, and -100 at ~2100fs to ~2250fs are probably the best compromise as far as recoil is concerned...still stout, but not bad in a 11# BC and the 458 American (45-70) at ~2100 isn't all that bad in a 9.7# SMLE either.
I would suggest you rechamber your 45-70 to 45-90 or -100 so you can benefit from heavier bullets and loads, if you want, while still being able to shoot the 45-70's. After rechambering my BC to 45-120(Magnumitis still has ahold of me) I wouldn't recomment that to the average shooter...unless you plan on going after the big bears, it's just TOO much, but the 45-90, -100 is plenty for 95% of all NA large game and essentially almost the equal of the vaunted 458 Lott in the NEF.
Just something extra to think about.
Luck