I had mine done on the red RS i had by Ringwood Speedo. They actually remove the voltage stabiliser and replace it with an electronic one. The only annoying thing was that it had to be cable tied up behind the dash.
Worked perfectly though.
Be careful testing the guages with the dash out of the car. The guages are only 5 volts not 12 and can be easily burnt out.
G
P.S. about bloody time you got this car going ... Will it make it to the club cocours at the end of the month?