We usually measure to the center of the star on the wheel. The idea is to eliminate tires as much as possible from changing ride height. 3/4" seems excessive for side to side, I think 1/2" is max. allowed. There are spring pads under the springs & big subframe mounts that bolt the subframe to the frame floor. However, these usually last a LONG time. If a subframe mount broke you'd almost certainly feel it in the ride. I'm not very familiar with the self levelling suspensions.

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Brian Toscano