I drilled a whole through on the drivers side. Easiest way to do it is to get a "step-up" drill bit, kinda looks like a cone shaped bit with ridges on it. Make sure you get one of the good ones though. That way you can drill it to any size hole you want. Just make sure if you drill a whole through the firewall or run through any other holes that you put a grommet on the wire where it goes through the firewall. And as always don't forget to fuse it within 12" of the battery..