I did this about 2 years ago, so my recollection may not be totally acurate. Separated the lower ball joint from the spindle. Yes, this may damage the ball joint, but I was replacing mine anyways. At this point push down on the lower arm; the bushings have plenty of give. Pull the old springs out using some kind of pry bar from the bottom of the spring; it will snap real hard when you get it over the bump. You may be able to use a strut spring compressor to get the springs out. I put lower springs in; they went in with only a push.
From: Raul Alvarez
All 3 times I've done it, I've removed the front springs by disconnecting the upper control arm instead of the lower -- mostly because I wasn't able to get the bolts out of the lower control arm. Plus, this way I didn't have to disconnect any of the ball joints. I also did not have to drill out the rivet for the brake line.
I disconnect the upper control arm while supporting the lower control arm with a jack. I also disconnect the steering tie rod end from the knuckle. The hub, brake, and upper arm assembly pivots on the lower ball joint and swings somewhat out of the way. Then I lower the jack which relieves most, but not all, of the tension on the stock spring. Then I use a pry bar or really big screwdriver to pop the bottom of the spring out of the lower control arm. It sproings against the back of the brake, but it's not enough force to cause damage.
Installing sport springs is easy because they are short enough to fit without much strain. Reinstalling the stock springs is hard. I position the top of the spring first. I insert a pry bar through the coils near the bottom, then use two jacks to lift the bar and the spring enough to pop it back into its position on the lower arm. This is very tedious and may require more than one try to get it. Then I use a jack to raise the lower control arm enough to reconnect the upper control arm and tie rod end.
From: Dave Nelson
You don't need a spring compressor for the front springs.
Remove the wheel.
Raise the car with a jack and lower it so that the inside part of the lower A-arm is supported by a jack stand.
Disconnect the bolts that connect the inside part of the A-arm to the frame. Disconnect the sway bar mount.
Disconnect whatever other items may hinder the movement of the A-arm, which is still connected to the steering knuckle via the ball joint.Remove the shock. [probably not necessary on 84-87 models]
Raise the vehicle with the jack until the tension on the spring is low enough that you can pull it out with your hands.
Replace it with the new spring.
Lower the car so that the A-arm is in the right position to bolt back up to the frame.
Re-connect everything that you disconnected and re-install the shock.
I used essentially this procedure several years ago when I replace the springs on my '88 GT and had no problems. In fact, the rears proved to be more difficult because they necessitate the removal of the struts and require a spring compressor to get the springs onto and off of the strut. Plus the rear end needs to be re-aligned unless you're extremely careful in marking the position of the strut.
From: David G. Mack