Jerry Noble, Illinois, has put out four paperback books on southern longrifles.
Dunno if he still sells them or one must pay amazing prices for one on abebooks.com
Single best article is the one by the late Robin Hale, Tennessee Rifles, a paper presented at the Fall, 1970, meeting of the American Society of Arms Collectors, Houston, Texas. My copy is in the bound (paperback) LONGARMS IN AMERICA VOLUME II, compiled by George E. Weatherly, from the ASAC
Also look at Cowan's auction site for past auctions, maybe two years ago they had quite an array of Southern rifles.
Do use a fairly late English style lock. Germanic locks (e.g., Siler) were rarely used in the South. Pennsylvania guys were all German anyway & bought their locks from Germany. In the American south the connection was with England, culturally and for locks.