The kits to restore the G45056 cylinder for the power steering are:
G45077 Kit-valve seals
G45078 Kit-ball stud
G45079 Kit-cylinder seals
It's my understanding the kits are no longer offered by case anymore. You might have a company that rebuilds hydraulic cylinders look and see if they can come up with the important parts. It looks like its operated more by O-rings than anything.