The front end is completley different, of course. Turbo is different, diesel cat is different from petrol cat and petrol pipe has lambda probes in it.
As James says, there is a good chance the pipe diameters are different.
From the cat back the pipe runs are different, the petrol system has an intermediate silencer and different back silencer shapes and tailpipes.
The mounting points look to be in similar locations, but I'd not bet on it. Offer the petrol system up to the bottom of the car carefully and check out all the fitting points first.
I'd not try this unless I had a weekend free and a means of getting a proper TDI exhaust if the LC one didn't fit. Not sure why you'd want to do it in any case, there's no advantage I can see.