I am assuming it is because the Tip Assembly was pressed in upside down?
Rather than flipping the Tip Assembly over, to fix it I would flip the Lever Mechanism Assembly over. This can be done by unscrewing the tip, removing the spring and ink and using the largest disassembly punch (transfer punch) that will fit through the Tip Nut hole to tap out the Lever Mechanism Assembly. Then flip the Lever Mechanism Assembly over and press it back in. Good Luck on your repairs. - Dave
PS The other option would be to use a larger disassembly punch after the Lever Mechanism Assembly is out to tap out the Tip Nut. Then you can re-assemble both pieces back onto the blank.