Yeah I was gonna say 45-70 as well but then read on.

45LC all the way! You don't have to reload to get hi-pressure loads for the 45. Look up the custom loaders like Buffalo Bore (I shoot his 300Barnes load in my 45-70 Guide Gun for deer), Conley Precision, Double Tap ammo and several others as well. The 45LC can be loaded into a MONSTER MASHER when loaded in a levergun!!!