To three engine ferry a RB211 you have to remove the fan blades and fit a fairing over the core intake. It is proberbly much the same proceedure on the CF-6 and JT-9.
You can also ferry a JT-9 with the fan blades "Gagged". In this proceedure you tie the fan blades to the stators behind it. The approved tool for this looks like a very long passenger seat belt compleate with the buckle assembly!. I have seen "Shock, Horror" report of this in the "Gutter press" . You know the thing "Aircrafts engine held together with seat belts". But it is an approved M.M. proceedure for the JT-9 . The other thing with this method of ferrying is you have to gag the core to prevent it windmilling. This is done buy removing the hydralic pump and fitting a gag to the pump drive.
A "5th pod" is a whole different ball game!. The fan is removed and the core fairing is fitted in the same way, then a small pylon is fitted to the top of the engine and it is slung under the inboard wing. I have been involved with a 5th pod in my time and it is a long involved and expensive way of recovering an aircraft. I can see why airlines try anything to avoid doing one!. Eaven with the offer on hot and cold running over time I would not want to be involved with one again!!!.
Rgds Dr.I.