If there is a speed limiter, which most believe there is set at around 112mph, it will be in the ECM not the instrument cluster. If the ECM uses the VSS pulses to detect speed you could fake that fairly easily.
You could work out the theroretical maximum in 5th at say the 6200 rpm engine red line if you look at the gear/drive ratio and tyre outside diameter. You must have some people who can do that
If you had a good full battery and IMAC&C with current hacks which you saved until you were upto max IC only speed before engaging that might be interesting.
I would not want to do much over 100mph on the stock tyres though so that would be an issue. I think they are generally S
112 or T
Good luck. I'll put a quid in a sweepstake and I bags 120 mph as my guess.