For about $250 you can get a drop in L&R flint lock for your TC stocck annd a drop in Green mountain barrel. As said above, the lock is the key in flintlocks. There are some Italian made long rifle reproductions, but some have insufficient drop to fit most adult men. There are custom shops probably hundreds of theem across the country. You can get a pre inletted or semi finshed gun to finish yourself. Check out Jim Chambers, Cabin Creek in Hellam PA, and there are others. But such custom or semi custom guns are not"economical" Perhaps $800 and up. However, if you get such a gun, it is an heirloom and not likely to depreciate significantly, when compared to a TC or Lyman.