I searched around for info about this and didn't find any definitive answers but i gathered some info and tried this and it works with mechanical gauges.
if your putting gauges on the A pillar a good place to power them is the fog light or cruise control switches.
Both switches have a purple and orange wire, Purple is positive and orange is the ground.
Apparently there is a current in the orange ground wire that makes the lights dim.
So crimp the gauges ground wire to the Orange and your gauges will dim with the rest of the console lights.