Looking for advice:

On my 98 Grand Cherokee, there seems to be a bad, or loose ground wire.

I figure that it's the ground wire, and not the headlight switch
because the dash / radio / VIC lights change brightness randomly, and
will flicker when I hit a bump in the road. I changed the headlight
switch about a year ago, so, I'll trust the switch is ok. The
flickering happens at all different adjusted levels on the headlight
dimmer switch.

If I hit the bottom of the dash, below the steering column, with the
palm of my hand, I can make the dash lights flicker. This makes me
think it's just a bad ground connection somewhere.

Before I start tearing the dash out of my Jeep, can someone suggest
where the ground wire attaches to the chassis? I'd rather tear into one
location, and not tear the whole thing apart to find a single wire.

Thanks.