No, I'm not sure, but I believe I measured correctly.
I am using the dealer spreader and set it up as pictured in the FSM:
Imagine that the case spreader U-shaped, with the top of the spreader in line with the case holes for the dowel pins. The turnbuckle was in the middle of the spreader and the solid piece at the bottom. I put the magnetic base just above the top of the dowels, inboard on the flat surface where the differential cover goes. I spanned the case and put the dial indicator pointer just inside the cover part. I watched it slowly increase from .001-.006. I was hoping to go .012 which was the bearing preload on the bearings at last install.
At .006 I could not easy remove the carrier, so I don't think it was overspread.
I am tempted to cut the box end off my 1-1/8" wrench so if I put a pipe on the end, there isn't much slop. Do you think a normal 1-1/8" wrench should be able to do this easily?
I don't have a lift. I was supporting the frame and letting the axle droop so I could get both the spreader in, and the magnetic base/dial indicator in to take the reading. Without the axle drooping, I wouldn't have been able to fit the dial indicator. This left the spreader about 1" off the ground.