Mine is in the same spot as JHM's. It was mounted with one of the metal rectangle hold-downs and kept the battery in place following a mild t-bone with a 4-wheel drift into and over an island, and then down an embankment. (Not that I recommend that as a test )
The (+) cable runs along where the floor meets the door-frame on the passenger side, and the ground has a custom frame bolt location for Ground (prev owner did all of this). I'm probably going to put one of those jumbo battery disconnect switches for a little bit more theft-resistance.
JHM suggested a sealed battery, but this is actually a MUST!