Oddball body tags do occasionally happen. I have an XE falcon sedan that has a build plate that says it's a XD. It was one of the first of the XE's made and has coil springs in the back not leaf springs so can't be an XD.

My dear friend, I had the same trouble trying to find out the very same thing. Well your troubles are over. The Y on your compliance plate unfortunately does not mean you have v8. What you actually have is fuel injected 4.1 litre 6 cylinder. Sorry to break to ya. But if that last digits a C she's a six m8.
Hope this helps