you want to swap the engines? or the cars? there would be no point swapping the engines as you could just buy a tdi one for less than it would cost to convert.
He wants the 1.9TDi engine , not the 1.4.
where does it mention anything about the 1.4?
i'll second the opinion that; you shouldnt build what you can buy.
Where can you buy an Arosa 1.9 Tdi ?
Might be easier to check if someone has done it on a Lupo
Easier said than done, especially the re-wiring.
Just takes some thinking, nothing more.