WTF did I buy?

Bought a 520i E34 touring that has been allegedly and mysteriously engine swapped with a 2.5 liter M50.

But I think the seller is either lying or wrong.
The block isn't attracting a magnet, and it has a DME MS41.0. Also the headers look m52.
The valve cover, engine cover and intake looks like M50 though.

Is it possible to build a frankenstein-m52 with m50 valve cover and intake, but use m52 for the rest? Maybe trying to hide the engine swap from TÜV?
Also should I be mad or excited for that?
I'm also trying to figure out the actual displacement, because obviously the seller's word is unreliable.

More pictures coming.