You mean Andy, of course, right?
I have a 48" jack, and it goes along the inside passenger side (tucked next to the rear wheel well "****"). I was thinking that a 60" jack would fit the same way, or otherwise place it diagonally across the inside of the cargo space. Pack around it so you can get to it...I have a "custom" mount set up on my plywood false floor that holds it pretty secure, yet allows me to get it out of there if I should need it.
For this, I have a U-bolt that the top of the jack fits into, and the base is wrapped in a towel to minimize rattling. Severe bouncing last weekend on rocks and hills made it jiggle a little, but it didn't bounce around -- there's an advantage to the weight of the thing, since it hardly moves!
Or get the spare wheel mount like Mike says, and only use it while wheeling (additional weight on the rear door, etc., etc.)
Andy