Yup. Propane torch.
No need for anything hotter, and move the torch around so you evenly heat the entire shell. The rubber will just about self-separate. The outer shells DO NOT get removed from the control arm.
'Course, first you gotta knock the end-caps off the bushings. A long punch from the opposite side, and whack it with a hammer. Clean-up the end-caps, you'll have to re-use 'em along with the inner sleeves, and the outer shells.
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If this was me--and it was, on my '97 K2500--I don't see much point to deliberately destroying brand-new rubber bushings to install brand-new Poly bushings.
Don't get me wrong--I love Poly bushings. But I don't understand removing perfectly-good parts to substitute perfectly-good DIFFERENT parts.
I'd install the arms with the new rubber bushings, and worry about installing the Poly bushings in five or six years, when the rubber has deteriorated. Good time to verify the ball joint, too.