All the cars I have dealt with, The "external" turning radius stops are cast in "nubs" in the lower ball joint assembly. At full steering lock, these nubs will touch the lower control arm. My bonehead engineering tells me that having these to limit the travel is preferable to internal stops.
I have taken a grinder to those ball joint stops to get a little more wheel travel.

Back to your topic;
If the wheels do stop at about the same distance from the frame, then technically the range of steering is equal for the left and the right. Shimming the steering box may result in a 1/4 turn reduction from one side, adding that same 1/4 turn to the other, ending up with an equal amount of turns lock to lock.