I do know that I drive torque, while listening to my friends prattle on about horsepower.
I've never actually tried swapping gas to diesel caps but I would suspect they are the same. Obviously the tab vs threaded ones will not interchange. One thing to be aware of is that the diesel needs a vented cap and most gas ones are not vented.
I haven't studied the mk1 fuel tank, it may be vented some other way then the cap.