Hey Paul. Have you heard Oscar Aleman's version of this tune? It was the sole inspiration for Garcia and Grisman's version. Really great. It is also in the key of Dm similar to the chart that man0a found. Have you found this chart useful?
The OP, @PLFishman was interested in a chord melody arrangement of this song. I took some of the ideas in the Dm chart that @man0a found and ran with it. I made some departures from the chord choices outlined in the chart, but not too much. This video runs through how it sounds singing, fingerpicking, and strumming. If anybody needs more details, I will be happy to share. It is a great tune and a lot fun to play.