Those old pine boards may be heartwood pine (also known as long leaf
pine) . We found this flooring in our house. I did some research about
it and ended up buying a small quantity to replace and fix some areas
of our house. We got it from http://www.heartpine.com/ they were very
helpful.

Make sure of the kind of cut you need: quarter sawn or plain sawn.

You may find that after installation, the color of the new pine is
lighter than the old one. This wood will oxidize with time an reach an
amber color. I suggest you not to stain it, just let it age. Ours
looked dissimilar right after installation, but after five months the
new wood is starting to blend with our old boards. The vendor told us
that after a year or two you wont see the difference.


--
raffo