DOOR LOCK KNOB – metal insert for threading

My '66 Newport came with new lock knobs to replace the crusty originals but the originals have a metal insert that allows them to thread onto the lock rod, and the new ones do not. I attempted to delicately remove said insert by prying, turning, twisting, etc., all to no avail. The new ones don't have any threads so they aren't going to work without that insert.

Anyone have a suggestion?
thank you!
Author: darth_linux