I think some difference is typical. Keep in mind that between driver, battery, alternator, power steering gear... there are several hundred pounds of bias on the driver’s side. Not at all unusual for the car over the years to be 1/2in + lower to the driver’s side.
Also remember that it only takes one part of the suspension on one side to raise or lower the entire side. Point being - JUST a problem in the front or rear spring will raise the car on BOTH ends.
A simple solution could be to swap springs side-to-side. Put the slightly more worn springs (front and back) on the other side.
To see exactly what is going on you need to get the car on a lift, a 4-post lift. Loosen all the suspension points (UCA shaft, LCA bolts, Rear leaf spring shackles, and front leaf spring eyelets) Not like loose so things are falling off, but you want everything to move freely.
As well remove the front sway bar end links and the rear sway bar.
Unbolt the bottom of the front shocks (so they come out the bottom). For the rear, it would be ideal to remove them as well.
Make sure all 4 tires have the correct PSI.
Sounds like a lot of work, but it's really not.
Make sure you have a full tank of gas, spare tire if you use it, etc.
NOW you have the car completely suspended only by the springs. Bounce and roll the car a few times to let the suspension settle. No difference in sway bar, shocks, etc. are in effect. Measure not just at the wheel wells, but also at the bottoms of the LCA, the rear spring perch, the subframe. See if you can determine exactly where the measurements are off.
If the car is still leaning with only the springs holding up the car, and you can confirm that the subframe isn't tweaked causing the problem or some other obvious variation between sides.. you have a couple solutions (in order from best to worst)
First you can put one or two of those twist-in spring spacers and see if that helps. Not really ideal, but it’s a fix.
Second try swapping springs like above.
Third would be a set of adjustable coil-overs. QA1 makes several varieties for our car. This will fix it but it’s expensive.