IIRC the blocks are similar but obviously the 2.0T is FSI and has a different cylinder head, exhaust manifold (part of turbo) and inlet manifold etc.
I've heard its possible to swap some of the 2.0T fsi blocks in to a
MK1 leon and then but the 1.8t head on. Reason it was done is because the internals are stronger as standard on the 2.0FSI engine.
So unless you want to find a way to make FSI work on a mk1 and then fit the cylinder head, turbo and inlet manifold its not worth it