The only switch that some older commodores had (on trip computer dashes) was the option of 60/80 L tank, for the working out of 'fuel remaining on the trip computer.'
Putting a VT 3 window V6 trip computer dash into a V8 will give strange readings also like '1200 km left' for fuel remaining and the rev guage will be out all the time.
The speedo may be as well, i think on the VXs and VYs they even changed the looms on the back of the speedo unit so that they cannot be interchanged with any units except their original ones.