I'm in the proces of changing the original back axle bushes by the strongflex PU bushes
The rubber needs to come out of the square metal part .. I've tried .. the center part came out but the sides seem to be molded instead of pressed like the e30 ones
You could shoot an email to the owner of Eurometric. He takes old subframe bushings as cores and refills them with polyurethane. Ask him how he empties them, lol