Suspension setup help Options

[75ninefourteen]

I've been researching the 914 suspension (factory setup) due to the fact I noticed my car was lower on the driver side. I want to make adjustments prior to getting new tires an know this should be set before getting an alignment. Plus I would like to try and understand the modifications made by POs.

Details:
* '75 914 with 1.8
* Springs/Shocks replaced on 6/23/00 at 45,881 miles (~68k miles now)
* Springs changed to 100#
* Bilstein Shocks (F4-B46-0179-H0 == 24-001793)
* Shock is set to the top most groove (6 grooves total)

As of right now, I've adjusted to get fender heights match side to side when comparing the front or the rears. I should also mention the rear fenders are about 1.5" from the top of the wheel rim.

Taking a measurement from the "donuts" on the underside the front sits 1 inch higher than the rear. (Front == 6.75" and Rear == 5.75"). I still have some adjustment left in the front to lower, but not sure how low the car should be lowered. My understanding is the rear should be slightly higher.

Center of the wheels measure right at 12" and the torsion cap is 7.5" (center to ground). Based on the manual I should technically need to raise the front to get back to within factory specs, but I know the car isn't running factory springs.

From what I've gathered, this current setup might have been more for autoxing rather than street driving.

All that said I am trying to get some clear answers about factory setup:

* What is stock height and where should I get a measurement from?
* To raise the rear suspension height, is to adjust the shocks and spring location? I have spare shims for the trailing arm, but if I am following correctly this is only for alignment purposes.
* What's a good way to see if rear shocks/springs are wore out? Pushing on the front bumper. I feel like the fronts should be replaced. So my guess is the back is probably due to be replaced after 25 years.

Thanks for the help in advance.