What size wire? I've run systems a couple different ways. The way i like best is to run grounds to battery AND the chassis. But I've found that a quick and effective ground is to put a ring terminal on the ground wire and find a bolt, usually in the wheel well or under body paneling, just make sure it's bolted to the chassis (bolts, not self tapper screws). Clean off any paint, bolt the ground where you found the bolt, and good to go. I've personally never had any problems with doing it this way. I wouldn't recommend this with 0 gauge though.