Welcome to owning a Ford. Your idi diesel has a oddball international bellhousing pattern on the block. So it has a adapter on the back of it to change the pattern. If it's in a school bus, dump truck, u haul, etc. with a big truck transmission, it has a adapter to adapt it to a SAE bellhousing pattern.
So Ford takes this engine and makes their own adapter. You would think they would have made the adapter to fit the 460 big block pattern they are already tooled to make. No. They decide to make an adapter that adapts to a completely oddball pattern. The c6 housing has to be re-tooled for this pattern, the zf and the E4OD all have their own special castings just for this oddball pattern they came up with. It has to be something political in it all.