ex_rigger
I imagine the Belfast was "hand made" like the Britannia. Parts like engine cowlings, which were specific to one engine. Swopping them to another engine required hours of filing and bending and swearing to make it fit. I diverted to Malta on an east med when no 2 engine cowl started to dismantle itself and it took all day to fit a cowl from the spare Proteus stored in the MU at Safi.