do you NEED them no, but most people use them. Without them your springs will sit metal on metal and could make noise. I was going to get stock rubber replacements for my 95GT but they were pretty expensive so I ended up using the old ones. You could use poly ones but they are known to squeak and they will actually raise your car up a little.
EDIT: I think I misread your original post so disregard what I posted, lol
i just wrapped the coils that would have touched other metal with duct tape. i dont hear any squeaking or grinding of metal. and it has a great stance.
These 6" tall pieces asist the center "snubber" in the event of a suspension bottom-out. If the car came equipped with them originally, It's a good idea to keep them or re-install them with new springs.