The steering box has a center position that can be seen by removing a plug. A pin is screwed into the hole which engages a dimple in the recip ball assembly.
The steering center also can be checked by removing the key and turning the wheel till it locks. If it locks with the steering wheel in the proper horizontal position then steering wheel is assembled to the shaft appropriately. If the box has never been off then this will place the steering in the center for most purposes. From this centered position the wheels are brought to the proper toe by adjusting the tie rods.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician