Where is the ground at the back of the passenger's head? (on an LS1)
 

I'm going to install an Innovate LC1 wideband on my 1999 Z28, and in the manual it says it's best to ground the LC1 onto the engine.

Therefore I was planning on grounding it at the back of the passenger's head (this is where the PCM, among other electricals is grounded), but where exactly is that ground? Accessibility there is nightmarish, I've felt the area with my hand and I didn't feel any bolt... so it's probably too far for me to reach. Where is it? If it's so hard to access, how can you possibly attach anything to it? Please help...

The PCM ground is on the driver's side.
The tapped holes on the front of the cylinder heads
are also on the back of the cylinder heads and in the same places. (mirror image)

Thanks :)

Here's a photo of the back of an LS1 (it's not mine, I found this photo on the net). Please look at it and confirm to me that what I've circled in green are good grounding locations? If they are, I guess I'm gonna need to buy a screw... does any know what size? (looks like 10mm, could be wrong... I don't have my car here with me to check). Also, can I ground my LC1 on either side (drivers or passengers side) or is there one that's better?

http://pagesperso-orange.fr/jpdesvau...1groundLS1.jpg

Either of those is fine.

Thanks, good to know.

You can probably see it from below the car...maybe with a mirror.