991.1 g series 3.8 litre engine v 4.0 litre RS

[Aikidoka]

When I had my engine replaced under warranty with a g series engine the engineer showed me the difference and it was marked. He said they could not get it wrong again and is was similar to the 4 litre RS engine (it looked very different to my old engine).

So, the question is how similar is it to the 4.0 litre RS 991 engine? Is the capacity different on the bore or on the stroke?

Thanks