Sir,
By stating that you want to stay away from production guns....I gather that you want to invest your money into not only a reliable functioning gun but also one that is historically correct. If an English Carolina trade gun is something that you might consider here are a few names for you.
Micheal Seidelman, Jack Brooks, Mike Brooks. Yes these are expensive builders and the wait may be longer but....you will be very happy with the finished result. You are paying not only for quality gun parts but the experience of the builder with attention to fine details such as....correct barrel length(46" rather than the standard 42")a proper profile barrel, ect.
Many will argue other wise but if I spend close to $2,000.00 for a gun, I want it to be extremely close to an original gun .....good luck in your search.
David