I guess you need to wait and see what they do. Since the cabbie is a "rare" type yours in most likely the first they have done using the information they had on hand. I would hope that now that you have given them the measurements in your letter they will make good.
You might also want to send them this link from MARC to show them that the slant window was only made in '31.
http://www.modelaford.org/technical/...s30-31open.asp
Good luck, remember that any merchant can look good when things work well but the proof of an exceptional merchant is how well he handles things when things go wrong. (My Dad told me this a long time ago).