Since all the write ups I found on removing/installing springs are on Cobras, I decided to do one on an actual Mustang
1) loosen wheel nuts
2) Jack side you wanna do first up
3) Remove wheel
4) Unscrew both brake bolts
5) Move brake out of the way behind the shock over the spring is a good spot)
6) place another jack under the A arm, right under the bottom of the spring.
jack A-arm up just a little bit to release pressure on the Upper control arm.
7) Remove bolt on Upper control arm.
8) Remove ABS line out of the way by unscrewing the bolt that holds it to the shock mount.
9) Now remove the large two bolts that hold the shock to the A-arm
10) SLOWLY lower the A-arm by lowering the jack as much as you can. If needed, raise the car even more on the original jack to allow the A-arm more travel.
11) Now remove spring. It may be stuck to the A-arm if the ISOS have rusted, so use a pry bar to release it, and pull it out.
Now its time to cut the spring. Use a grinder (can be purchased at Home Depot or Lowe's) Cut no more than 2 coils. between 1-1.5 coils for the front springs is recommended.
Reinstall ISOS if wanted.
12) place spring back in place and start jacking the A-arm up. Make sure the bolt on the control arm lines up where it needs to go
Now reinstall the bolts on the shock, control arm and place brake back in place.
That's it your done.
Now let it sit for around two weeks and if you like the stance go get an Alignment.
Hope this helps some people out.