For anything in NA, the .45/70, even with black powder loads, is more than enough. Trapdoor Springfield-level loads of up to 28,000psi are more than enough, as they add a good 500fps+ to the BP level velocities. A fun one to have, would be a .50/70 or even .50/90 in a DR.
-------------------- Daryl
"a gun without hammers is like a Spaniel without ears" King George V