Need a measurement

You know how on a square body the rear of the bed is higher than the rest, it like slopes up to the back. I was wondering if some one could get a decent measurement of how much that is. I know if they are layed flat the rear of the bed wont touch but in front of the wheels will. Any help here would be appreciated. I figure I need like 4 measurements. Very front of box, in front of rear wheels, behind rear wheels and very rear of box.

man your a pain

1.25, 13, 23, and .75 is what I just measured