As for the fans at the stern, little bit puzzled, yes it shows the motors and what appears to be a frame, but no fan, if you google images of centrifugal fans (the basic paddle type), its a ever increasing diameter body with an inlet on the centreline and an outlet to either the left or right vertically or horizontally to one side of the centre, usually in extract or supply fans they use backward curved or forward curved fans - similar casings but to suit bigger duct diameters, don't see where these casings are, as they would be usually on a frame like those you fitted, a more detailed historic photo might show how this are is laid out, but it would have to be closer than that, did the shipyard not take any while refitting / repairing?