Stevetrousers

Hi there I wonder if anyone would be able to help me please? Got this engine from a garage clearance, a customer of mine who passed away. His step son tells me it was a working engine v6 2.6litre taken from a damaged Quattro. Does anyone know how I can confirm what type of engine it is... ie that it is 2.6 not 2.8 etc. I want to advertise it for sale , obviously untested, but don't want to tell anyone the wrong info. Presumably there is an engine number somewhere? Thanks for reading, steve

V6 2.6 engine identification