Psssh, screw that, find some kind of torch and burn them out like darian said then take out all that built up anger and let it loose on the collars any way you can. Then use the C-clamp method to press them in.
Bing has a special on his aluminum bushings right now, they will create a stiffer ride and more of the noise from vibrations will be emitted to the cabin, but if your willing to sacrifice that then go for it. otherwise the only “subframe bushings” actually made for our cars are just inserts, so you will still need your old ones in there.
I do however remeber reading someing about the Z32 polyurothane bushings fitting into our subframes fine, so you may want to look into that if you dont want to go the aluminum route.