Interesting Tombie, because if you try and buy a KNB500023, you are told it has been superseded by LR040248, like here KNB500023 | LR040248 | TOWING BRACKET ASSY USA+CAN G-CAT | Land Rover | | Britcar (UK) Ltd
So you can clearly fit the D4 part to a D3. And a number of places have the KNB500023 labelled as fitting the D4 like this one Land Rover Trailer TOW Hitch Receiver Genuine Range Rover Sport LR3 LR4 | eBay

