Chances are the original rubber bushings are as hard as the steel they sit in. Use a torch and burn them out. You will have to support the frame on jackstands so the axle droops. Undo the shackles and use lots of fire to destroy the old bushings.
It takes a little work but nothing too tricky. I had one bad bushing that caused a clunk when I turned one direction. I replaced the front with the poly ones and greaseable shackles amd it made a nice difference. I've got the rears but I have not got to them yet. It helps to use the bottle jack that came with th 60 to help allign the spring holes with the hanger holes when putting things back together.
sawz-all...cut right through the bushing AND the bolt...takes about 5 minutes. new bolts are cheap compared to the time it takes to remove the old ones.