1 hour ago, Jason240z said:

I'm now leaning towards an early e88, or e31, looks amazingly similar to my e31.

That small mound around the plug looks a lot like my E31. My early E88 has a more pronounced hump but that could easily be ground down. 

I think you are right. Nice looking head in my opinion.

Grinding the code off could also be a clue. Someone trying to pass an E88 as an E31?

Of the other way round.

 

nicely prepped though. 

Its a mystery!