Just last weekend I installed lower spring caps from JohnB on my 2000 GTS (non ACR). I will say it is very easy of a job, infact placing/removing the car on jack stands and removing/installing the wheels takes up half the time.
1)Plan to remove the shocks, it is very easy to do and they are much easier to work on the bench. In five minutes I realized trying to compress the springs on the car was not practical using the spring compressor I had. The front sway bar will also need to be removed but it comes off very easy.
2)Rent a mcpherson strut compressor from a place like AutoZone, etc or buy one for about $50. They are pictured in the photo from KNG SNAKE. There is nothing unsafe about using these. I found that they attach very securely to the spring coils and it would be very difficult to have a failure. Place them opposite one another on the spring and alternately tighten each by a few turns at a time.
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3)Now would be the time to adjust the rebound of the shock. On my shock body there is a +/- indicating the direction of rotation for the adjustment. The spring does need to be removed from the shock to do this. Again, this if for a 2000 GTS (non ACR) with BLUE colored Koni shocks. I plan to remove my shocks again and adjust them to two turns as recommend above.
Koni adjustment instructions.
4)Install the new caps and release the spring compressors in the same manner as they were tightened.
5)Install the shocks on the car, I had to leverage the suspension down slightly to allow the shocks to slide into their mounts.
6) Ballast the car per the service manual with a full tank of gas, 165lbs in each seat and 70lbs in the cargo hold and place the car on it's suspension prior to torquing the shock bolts.
Here is my solution to the last step. I had a helper (approximately 200lbs, which was half the 165lbs plus half of the required rear weight) set in the driver's seat while I placed my floor jack under the front control arm to raise the suspension until the front corner of the car came off the jack stand approximately 1". I jostled the car a few times and then torqued the front shock bolts. I repeated this on the rear and then had my helper move to the passenger seat while I repeated the process on the passenger's side. Not exactly per the factory service manual but close enough and I have had success with this method several times in the past on my BMW and MB suspensions.
I would highly recommend to ballast the car and torque the shock bolts under load. The suspension will compress nearly twice as much with the added weight as it would under just the car's own weight.
I took it for a drive afterwards and noticed a HUGE difference in the tracking of the car, it no longer followers the ruts in the road. This means the alignment HAS changed front and rear. Most likely now being lower there is more negative camber which will also cause the toe to move outwards. I have an appointment for an alignment Monday and I will take note of the numbers. At this point I would say an alignment is highly advisable even for the .5-.75" lower curb hight from the spring caps.