Hey Chris, You are referring to the holes that rotate the diff housing up and down between the bulkheads..On the rear the plugs go in the top hole to rotate the pinion of the diff down because the rear suspesion angle is not as great as the front..Now the front plugs will go into the bottom hole to rotate the diff pinion up due to the front suspension kick-up. these plugs are designed to keep the drive shaft to diff pinion angle as straight as possible...

I hope this helps-Have fun!!