ba53,
Marshall plagiarized the German proto-neoclassicals on a bunch of major ideas. They should have sued him.
OP, first, you should politely send a letter to the author. Possibly he did not recognize your publication (Public Choice) - But, if he did not cite your working-paper version on purpose, I bet you win. Second, if the author ignores your polite letter, contact the editor with very specific reasons why his work is plagiarism - Be careful here: if it turns out you are perfectly wrong, e.g., the author cited your work or the model is not exactly the same as your arguments, then YOUR (not his) reputation in academia will plunge to unseen bottom.