I'll 3rd the Lyman Great Plains rifle, or even one of the less expensive Lyman Trade Rifles.

The GPR can be bought assembled or in kit form. Left or right handed, flint or percussion, round ball twist (1 in 60 or 66) or a conical/sabot friendly faster twist rate.

The trade rifle is a 1 in 48 deal only - mine does phenomenal with balls, will shoot heavy conicals and sabots acceptably.
I think it can be had in percussion or flint.

I hate Pyrodex.

Have a good day man. In honor of personal freedom and the open squirrel season, I think I'll go put a hole through dinner's head.