The Lyman Great Plains Rifles are a terrific choice. I have shot the 1-60 round ball twist with patched ball, and the Hunter model with the 1-32 twist which works great with conicals like the Lee REAL, T/C Maxi-Ball ammo. Killed a lot of deer with the 50 caliber round ball and 90 grains of FFg powder in Florida and on the farm in Georgia. Hogs as well. Generally shot from 30-90 yards as that was what the terrain allowed. Only had to track a few animals as most of the time they dropped within a few yards, if they ran at all. I liked the round ball barrel the best as it was more traditional and more challenging. And it was VERY accurate. If I were in your shoes, I would go with the faster 1-32 twist Great Plains Hunter as you will be able to shoot both round ball and conical bullets. In my 1-60 twist barreled gun the few times I tried a maxi-ball, it shot consistently at 3 o'clock on the target. Adding /reducing the powder simply moved the POI further out or closer in from the center of the target. OTOH the 1-32 barrel ate the conical bullets like a kid in a candy store.
Get the Lyman GP Hunter, you will not be disappointed.