Obviously I should have done more research before attempting a ladder bar/coil-over suspension.

How do I determine centerline of the vehicle? Once it's determined, how do I find center on the rear axle and how do I ensure the axle is centered in the vehicle? I know I can't use the pinion as it is offset to the passenger side. That's why I thought if I just hung plum bobs off the rear frame rails and measured the distance to the axle flanges and made sure it was the same distance on each side that the rear would be centered. I already triangulated the ladder bar crossmember before welding, ensured the ladder bar brackets are evenly spaced on the ladder bar crossmember, and ensured both ladder bars are adjusted the same.