2G Dashboard grounds

[dfootedsm]

I have 2 larger grounds beneath my dash on the driver side of the car coming from the loom that goes that rolls into the Dash guages, is there a specify bolt they should attach two or should I Just use self tappers and drill them to something bare metal? .

 

[Detail]

It bolts underneath the dash, but above where the gauge cluster would be. There is a plastic piece of the dash harness that is right in front of where that bolt is. This is on top, not under the dash.