I will be ordering their 8.8, 31 spline LvL II kit, the u-bolts are 9.75” long I think by 3.25” inside dimension with a ⅝” dia rod size; the U-Bolts are the same length separate or in the kit.
Not sure if you can order separate u-bolts but I can’t believe they are not available.
For you just measure the spring pak height, and any blocks between the springs and the axle and the tube dia, add them up, add a couple of inches and you got it the length of the u-bolts.
Measure the width of the springs also while you are there if you intend to buy new Spring Plates.
4x4, 5sp, Std Cab, Stepside, E4 Red
4” Lift - Coil-Overs, 6” SkyJacker Leafs - No Blocks (Mistake)
31 Spline FX4 Rear Axle, 4.56s and OX Locker, Hurst Shifter w/Optional Stick and "Made by Grev" alignment adapter