I would start with a phone call to the reference librarians at the New-York
Historical Society *Library*.  They may have the 19th C fire
dept./insurance maps that I have seen for other cities. Or there may be
some other architectural sources that would be appropriate. In any event,
they will tell you if you are better off talking with the people at NYPL
Humanities Library (the main research library at 42nd St. and Fifth Av.).

Good luck!  Sounds like fun!

Judith Lee
Ohio University