I don't know if that's a calibration code or not.
As for making a 150 mph speedo work in other cars (or any non-stock speedo for that matter), it seems someone could design a two gear adapter to splice in either at the speedo end or trans end of the cable. The gears could be made to reduce or increase cable speed to compensate for the difference. A 10 or 20 mile drive using mile markers for reference against the odometer of the speedo you want to use would let you know the amount of reduction/overdrive you would need.
The problem with trying to do it with the speedometer is that the speed and odometer/trip gauges are controlled separately. The odometer looks like it would be easy to remove the gearing from your old odometer and change, but the speedo part looks much more involved. There is a good article on VDO speedometers at
http://members.ispwest.com/jkcaplan/Speedofaq/speedo.htm.