Stereo wire ground.?

You should have a ground wire up in there from the old stereo

As far as chassis ground, any clean metal spot should work. If there is a bolt or screw somewhere close, loosen it off, a little, bare wire goes around it, tighten the screw. You could probably drill a small hole, just be careful, then use a self tapping screw, as long as it is metal and clean. Don't drill into anything you shouldn't. Just my opinion.

Well I just bought this truck let my wife drive once and now my stereo isn't coming on and there is this black wire hanging from under my steering wheel. I have no clue where it goes?

I understand, but, I can't see anything from here. I don't know, I was just talking about chassis grounds. Hope you get it going your way.