fuel lines, ebrake cable, clutch cable, t-case boot, speedometer, gas tank filler tube and vent tube, brake lines(hard(back)flex-line(front)), axle vent tubes, radiator, power steering pump.
also include any accessorys like a/c or cruise control.
in my opinion, i wouldnt lift the entire body , but loosten all the body bolts, any rear brake lines, the gas filler and just jack the back up watching carefully the fuel lines under the battery area. you should be able to get 6" or 8", but 12 is stretching it.