Here's my opinion of all longrifles kits as generally compiled with regard to anything TN or "Southern" (as I don't know all the fine points of many other schools), and as they were offered a few years ago when I was perusing them regularly, and with notable exception to Jim Kibler of course, who sells something entirely proper and is in a different class:
Learn the style/school of rifle that suits/interests you best. Find a kit with as many proper parts and pieces as possible included. Then, this is the very important part if you'd like your gun to not scream "I BOUGHT A KIT" to anyone who sees it and knows longrifles, be SURE to put an English lock on a Southern/Tennessee gun unless you are emulating a specific exception to the rule (not likely if you're buying a kit with odd parts). For some reason (profit I suppose) most all kits named "Southern Mtn (yes a wildly generic term) or "Tennessee" were bundled with a most things proper, but a Germanic lock.
If that is indeed still the case, I'm pretty sure most of those companies will allow for a substitution of an English lock, but generally they'll throw in a Siler. The Siler lock is a perfectly serviceable lock preferred by many, but Southern Originals nearly always had an imported English lock for ignition.
Additionally: If you're handy with wood at all and have some time and space, leave off the precarved stock and get a blank, cut it to profile, let in your bbl (or hire that bit out) and have all that great wood to clamp, carve on, and fix your mistakes with. Margin of error is very slight when using a pre-shaped stock-and not all the errors will be yours.
Excuse my mild rant, but I expect kits (for Southern or TN guns) haven't changed and is why I never bought one.
Also, look up pre-carves and swamped bbls posts and see why craftsmen tend to hate pre-carves and shooters tend to hate straight bbls. Get the right parts, you'll be much happier in the end, no matter how slow the process or "expensive" it might seem.
Cheers.