Those springs are legal, and look good. They definitely aren't too low. I could put them on a car in under an hour at midnight, maybe even beside a busy road. It's an easy job.

1. Jack up car and put it on jack stands, hang back wheels down, don't put stands under diff. Don't jack it up too high. High enough to just lift the back wheels off the ground.
2. Put a second jack under the bottom/centre of spring.
3. Undo the shackles one at a time.
4. Let this detached side of the diff go slowly to the ground.
5. Undo the U-bolts holding the springs to the diff.
6. Put the new springs in and tighten up U-bolts. swap over the shackles. Don't fully tighten all nuts and bolts until the car is back on it's tires.
7. Jack up the diff and reattack the shackles to the body.
8. Do it again on the other side.
9. Go around and make sure all nuts and bolts are tight.

They are fantastic springs. Don't waste your money buying new ones..trust me

I only didn't need them because of going for 4 link. No dodgyness involved.

Chris.