The first task is to figure out where to mount the battery box. It should be a flat, level place that's not so tucked in that the battery can't be removed easily. At this time, you should study the underside of the car to determine if the holes for the battery box retainers will be accessible. Watch out for the gas tank, leaf springs, and other undercarriage items that can get in the way. Sometimes there will be brackets in the way that will need to be removed for proper installation.