It has to be one of the "L" shaped mufflers as a minimum, but ideally from one of the 70cc saws. The 70 cc models have deeper fins for better cooling and so the simple pancake mufflers from the smaller 10's won't fit, and the 82cc saws have a pattern all their own.
Also keep in mind that the mufflers intended for the DSP saws (3-10 DSP, 5-10, 6-10, and early 7-10) will have an extra hole in the back (against the cylinder) that lines up with the vent off the DSP valve)
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Mark