I would suggest you re-evaluate your pricing, I think you are way under valuing them. Not sure what research you did, but here is a good source on the history of the 715 Lemans carb; SAAC-29 (wildapricot.org)
You might try reaching out to the Shelby forum for more info on these...there are some very knowledgeable guys on all aspects of Shelby equipment.
Nice pieces. The four digit dates will mean 70's+. IIRC the change was '73 or '74 to 4 digits. A serious buyer will want to make sure about the #'s on the blocks as well. Heck, Im curious myself.
Im mixed about your price. I would like you to get more for the vintage but they make brand new ones as replacements with SMS numbers. www.cobranda.com doesn't show a price now but carls has new ones for $1395.
As explained in the link bsolo66 provided, you can tell they're reissues by the (unused) boss between the secondaries for an accelerator pump nozzle (in case the casting is used for a double pumper application). Nice carbs nonetheless.
As for the price, you're asking half of what a new one costs. Maybe not unreasonable?