The book is titled The Book of Lancaster, Carving Details for the Gunmaker- Full Size, Presision Carving Study of Original Longrifles by Susanne Warren-Bicio. I do not see it on Muzzleloaders Builder's Supply website, but I may have searched too quickly and overlooked it. It contains full size drawings by Ms. Bicio of the carving of 26 original Lancaster makers. A bonus is that you get to see (clearly) other details, such as patchbox engraving, buttplate profiles, entry thimble configurations, etc., wherever they happen to be adjcent to the carving. Her drawings are superior to actual photographs, to my way of thinking, because (1) they are full size and (2) they depict depth more effectively than photographs.
Ms. Warren also sells a book entitled The Johnson Record which is a collection of original carving and engraving patterns by Dale Johnson. The only drawback to that book is that many of the patterns are not attributed to an original maker. But a student of longrifles, with other reference books, will be able to do a match-up.
Ms. Warren has a website: historicalarmsmaker.com. She is in Arkansas. You can order directly from her by mail. Her Longrifle Construction Manual is excellent, especially for architectural detail- the small things that, when put together, make a longrifle a work of art.