It won't be so easy to install the swivel base. I think there was one before, through the hole on the plate, but if you get a new one you will realize (i think) that you can't disassemble it and just insert it trhough the same hole. You will proabaly need to take it to a workshop. Or if you itend to keep the rotating base of the new one and install it above the plate on the traveller, check that it doesn't end up too high.