He probably is talking about the diameter of the axle.
I just replaced my leaves and the u-bolts are 3 1/4" round top. I got 10" lengths since I used a 4 leaf 1750 lb per side spring with an AAL.
I got about 3" without using shackles. I may put the shackles in, they're sitting there in a box, to get another inch or so. The torsion keys gave me 3" of lift in the front with the adjustment bolts at the original depths. I turned them out so that I'm right at 2" of lift, and the front is still slightly higher than the front.
I have to put the RS5374 shocks in tomorrow, to smooth out the ride some. The Ranchos I have in there now are to short and it does compromise the ride. The coilovers shocks in the back still had to pushed up with the floor jack to get them in place, so they should be ok.
I've ordered SportTrac end links for the rear sway bar. Once they come in, I have an Explorer Express rear bar to put in. I have to change the front links also, I'm sure they're to short now.
I have the BW4406 and all of the parts just sitting and waiting for another long weekend.
Once you start, you can't stop.
MT