If it were me. All said. I'd do it in 45-90. You can still shoot 45-70 ammo in it. In almost all cases the boolit is already in the throat before the base has left the case mouth if using a 45-70 in it. Best of both worlds. Shooting black or smokeless, jacketed or cast, light or heavy for caliber. Lots of options with this caliber and not an expensive one either. Loaded for fun at the range or loaded with serious punch in the field. Yup, that's my two cents worth.