You could drill a hole in that shock to drain the oil, then compress them in a press. But you will have to strap or weld the shock to keep in collapsed, they are spring loaded. That will also mean the shock is storing compressed energy, and if the strap or weld fails it will expand violently.
Someone here cut them apart to remove the spring, but honestly it would be easier to get some bar stock and make a bracket at that point. It’s literally just going to be a piece of flat stock with another flat plate on the end to mount the bumper.