Nope, the relay boxes are not interchangeable, but the motors themselves are identical. If you take the fan motor from the diesel and wire it up to the petrol relay diagram I have posted, then plug and play
You can probably do that Mr B. The relays will be the same and the spade connectors on the wiring . It's just the diesel one incorporates a pcb, the petrol one is as per Artic's picture on the other thread with just two relays .