The original part had a metal ferrule/pipe in the middle and the rubber might have been vulcanized to the housing that is clamped to the spring-pack. There might be a metal outer covering around the rubber.

You have to press out the whole center section (rubber and ferrule/pipe).

Then, thoroughly clean out the "housing".
Then, freeze the new bushing and press it into the housing (I have used a little thin oil (MMM is OK) as a lubricant).