reference for adjustment of panhard bar(speedtech suspension)

[72Z/28]

Hi
Just wondering what is the proper location to be taken as a reference for adjusting or centering the axle via a panhard bar (speedtech suspension)?

I realized that the gap between the frame rail and inner tire on the passenger side is more than the driver side. The rocker panels also were widened a bit to fit 335 tires but I noticed the gap between the fender lip and the tire are almost the same on both the driver and passenger sides.

Maybe taken the gap between the tire and fender lip will be misleading due to panel installation

would appreciate your input guys