use a paint pen across every thing, put a straight line down the center, left to right or up and down don’t really matter. after installing the seal just line it all up. and its ok to re use the original nut and washer. and save a few bucks
The proper method is to pull the carrier and use an inch-lb torque wrench to measure the pinion preload. The next best method is to leave the carrier, pull the axle shafts, measure the torque required to turn the pinion/carrier before disassembly, and then tighten the pinion nut until you match that spec. Any method is better than just hammering it back together with an impact gun.