[Lynn Eades]

The mk2 is riveted construction and has conventional air ducting, as per other carriers. when you say "Mk3" , I take that to mean a Mk3w(Welded hull). The Mk3w has no air ducting as per your model. the air is drawn in through the std.large hole in the division plate(as per other models. It flows on through the engine area through the two rectangular holes in the rear plate( as per other models) The hot air is then turned up through 90 degrees by a curved plate that bolts both to the rear plate, and the rear deck (the one the jack bkt. is mounted on) The hot air flows up and out through the mesh screen.(the most rearward mesh on your excellent model)
I immagine the whole reason for this is to dramatically increase the carriers wading ability.
I have some cable reels made of panel steel with wooden centres. they fit the brackets on the carrier. They appear narrower than the one in your picture, but are the same as the one in the stowage plan I posted.