I am not trying to be a smart a-s, you have the car listed, you have provided pics, I don't see where you could do much more. If there is something in the pictures you provided that they have a problem with, you could take more detailed pictures. If I were them and really wanted the car I would hire someone, (an appraiser?) to look over the car, send me a report, deal from there. Being your in Texas it should be easy to get a shipping container dropped at your place, have the hired inspector watch the loading of the container and send it to the nearest port.
My parents neighbor sold an old Caddy to someone in England, it is fairly common.