Michael,
I'm guessing here, but I would expect this to be integral to the ECU. I dont think it is a mechanical gadget that you can just remove. In the UK we convert our cars to read MPH as opposed to KPH and this is usually done electronically, by altering a stream of pulses from a speed sensor. In turn I would expect this altered pulse stream to be fed to the ECU, tricking it into thinking the speed is slower than it really is. In theory the speed limit will work at 180mph, I doubt whether anybody will be able to prove this!
I would think all you need to do is buy one of these devices and fit it to your car, but rewire the speedo so that it still registers KPH not the new MPH, just feed the converted signal to the ECU. Be careful to do this correctly or your speedo will under show MPH on a KPH scale.