You need both a switched voltage and also to pick up the voltage off the dimmer for the lights.

You will not have a problem running all this on one switched voltage. I run a Trans Temp, Oil Pressure, Voltmeter, Ambient Temp, all off one wire from fuse 13. Same thing with the lights, have five gauges added to the brown wire in the center dash (small clock is on there also).

To make your wiring easier on the grounds, run a ground wire for the lights and one for the gauges from the center ground. Makes the wiring a lot cleaner, did it all on one ground the first time. Just replaced the entire rats nest with a new home made harness. Took longer to connect the grounds and power that it did to hook up all the gauges and the rats nest of wires has been tamed now.

Regards,

Paul