From time to time I have access to barn wood for sale. Most times I will just act as go between and pass on request to owners.
The following is currently for sale and is great selection of chestnut, mainly 2" threshing flooring that was splined and comes out of an 1879 barn, contact me for further details. There is also some old hemlock siding from same barn and maybe some 1" thick planks in chestnut!