You should go to Greg Adams' "Banjo Sightings Database" and sort thru the Boucher banjos in there. If you look at the information listed on each instrument, there are many, many measurements...a builder ought to get enough info there for a very nice reproduction.
For instance, here's one: http://www.banjodatabase.org/3DFullDetails.asp?ID=173&imgtype=u... Double Tension VIIII
All of Greg's dimensions are metric but we won't hold that against him. ;-)