You're supposed to re-use the metal end-caps. Smack them out with a long punch and hammer. Put the punch in from one side, smack the opposite cap off by hitting the raised ID of the end-cap.
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The Polyurethane bushing kits I've seen (Energy Suspension and Prothane) expect you to re-use the upper steel sleeves as well. They give you new sleeves for the lowers--you only have to re-use the pressed-in steel shell--but not for the uppers.
I had to whittle new upper sleeves for my '88 because the originals were so far gone due to rust.
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Stealing the metal parts from "new" rubber bushings would be the easy way. I have to make four more sleeves before I rip my '97 apart. It's not fun, because I don't have a lathe.