"There were twenty bloody scabbies there a-shearing in a row" is the way I've always sung it, rather than Banjo Patterson's words. That's how I heard it and it stuck in my mind - and it's a better line anyway, and a lot more singable. The point isn't that they were Chinamen, but that they were scabs. (And I'm a bit sceptical about that origin for "scab". I think the term just means that strikebreakers are excrescences that you'd be better off without.)

I remember Nigel Denver sang it that way - he used to say that it went down great in Ireland, especially the line about "Handy with the rope me boys, I'm handy with the brand." He found out it was because with the Castlereagh being the British interrogation centre, people tended to assume that the song was something to do with the interrogation techniques employed on prisoners.