Contact Tennessee Valley Muzzleloading.

http://www.avsia.com/tvm/index.html

they sell kits and the rifles and parts are top quality. If you go Flintlock, a Seiler or Chambers lock is best. Barrels.. there are lots of choices. Rice makes an excellent barrel. And for calibers they run from 45 to 62 caliber. So the sky is the limit there. Most of the kits are under a thousand dollars.