G'day Mark,I would be able to do you a MIDI of the version we (Selectors>/i> did during the '80s ... I think that is basically the Wallis & Matilda version, but transcribed by me from memory.
Wallis & Matilda are an Australian performing group (although I won't vouch for distant origins). They were on the bill of fare at The Australian Folk Festival at Kiama, June 1999 ... the best way to trace them or check details would be via Dave De Santi, the main organiser.
I could not find Clancy by a simple search of names - or by a lyric search on "overflow", so I guess it is not there. I will post the words (they are almost a decade out of copyright) and a MIDIText, but the POEM will be on any number of poetry sites.
Regards,
Bob Bolton