Tried the search, and it returned no results?

What needs to be done to convert a 82 SD from a 85 mph speedo to a 120 mph one?

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Jason

00 Subaru Legacy (fun wagon)
96 Nissan Sentra (disavowed)
82 300SD (garage queen, will run again hopefully)
87 300DT (Gone: 10/15/2010)