B747-200, DC10 and Tristar all carried pods. Their engine inop ferry performance was very poor, so engines had to be carried to the aircraft.
I have flown on Tristar ferry flights with an engine inop. It is not recommended, and the ferry range was about an hours flight with a RB211-22B, or two hours with a -524.
There are a few B744 that can carry pods, Qantas has the system. But with modern engines it is not necessary. A B744 can do a three engine take off ferry flight and fly for about 6 hours. We always ferry ours back to base.
With the reliability of modern engines it is just not worth it. It is cheaper to charter a freighter and fly the engine to the aircraft if necessary, than carry around the fittings for a pod all the time.