Hi, NJH - I don't know Greenbird, so I can't help you there.

There is a Website called Yet Another Digital Tradition (click) that converts our Digital Tradition tunes into pennywhistle notation. The tune for Woody Guthrie's "Reuben James" is Wildwood Flower (click), an old Carter Family song. The lyrics are here (click) - unless you're looking for this Reuben James (click), which is a completely different song.

-Joe-