GuestQ: not quite the amount of work you'd think. Cut'n'paste to 'Word', make small adjustments; cut'n'paste to the 'Cat.

Apropos the tune, your first posting slightly misrepresents Twain's position. In the intro I quoted he says "The idea (not the chief idea, but the vehicle that bears it) was probably suggested by the old song called "The Raging Canal," but I cannot remember now."

So whilst 'The Raging Canal' might give us a lead as to his original metre and scansion, I don't think we can safely assume that the final poem followed it slavishly.
It would, however be interesting to know whether anyone has heard the poem set to music.

Nigel