I was surfing around and this name, Allen Ludwig kept popping up. Mr. Ludwig photographed a huge portion of the important stones and the key to learning about him was through a university library website and the collection of originals that they have of his work. So, off to Alibris and then finally to Amazon to type in his name and find out that yes, his work and writing have been published as a book,
Graven Images, New England Stonecarving and its symbols, 1650-1815
Looks like I have something to read. Really Read. Jam packed with reference from very primative stuff, to portraits with lots of information on carvers, geography, art, handbills of the time. Sets this funerary stuff in the social context of the time.