Wanted to install a Aux battery in my 2k silverado, but upon further inspection, it looks like that's where Chevy installed the AIR pump for SMOG. Anyone in California or that has California emission standards installed an aux battery in their truck?

 

Get a sealed battery and mount it inside the cab somewhere. That would probably be the easiest since you dont have space under the hood due to smog pump.

 

This is what I did. Ran 0 ga. back to the second battery which was a Kinectic sealed battery. Built a holding area for it that pressed up against the jump seat, so if it needed replaced you could easily remove it. I took all of my stereo stuff out of that truck though, I don't know if I have any pictures.