Depends on what you want. Obviously you are not worried about period correct as gun of that type wan't made in a left hand version originaly.....though there has been archeological evidence recovered of at least one chief's grade fusil that had a left hand lock....poor s.o.b. probably had lost and eye or a hand. :shake:
Anyway, consider their fowler as it has a more forgiving stock design that should be more comfortable to shoot....Tulles are notorious cheek smackers. And since it's not a copy of any particular production model it would be more correct if you ever find yourself leaning that way....and it will have higher resale value if you ever lean that way instead.
The first question you need to ask 'em though is if they will supply it with a tapered barrel, both the octagon and the round section....I'm sure they can build it around a Colerain, no reason they can't. Guys have bought smooth bores off TVM before they advertised their "special straight barrel" and were very dissapointed in the gun because of its weight.
Word is that they are very accomodating, so should have no trouble working with you. Enjoy, J.D.