For mounting the perches on the axle just bolt it together just tight enough to hold it in place, but still able to move the axle for centering it. After centering put the weight of the truck on the springs as if to sit at ride height and rotate the axle to line up with the T-case. Double check the centering measurements. When all is good tack weld the perches into place. Remove the axle and fully weld perches.