Do you have a 4 cylinder or 6 cylinder engine 2PAC?
The rev counter wont read properly on the Carlton / Senator digidashes as they expect 6 pulses per revolution (6 cylinder engine) as opposed to 4 per revolution the 4 cylinder engines give out.
You could try and retro fit Astra GTE Digi dash, but these are much narrower than the carlton dash.
HTH