Last year I had a high voltage white Xpin display that I was using in SM and had it converted over to low voltage to use in our Mustang. Brett from Xpin emailed me these instructions:
Remove L1, the big black circular inductor.
Move R20 to location R21
Place a diode, preferably a schotky, on D2. Make sure to observe polarity.
I ended up taking it to John Juke's here in Vancouver and they converted it from high to low voltage for me (only additional part I gave them was the connector for the low voltage unit).