Need help about head & piston condition

[Camut]

As mentioned in my introduction post, I'm rebuilding a D24T to fit a 740 GLE Polar.

The car came with a spare D24T in it. This one's really smokey.
The original motor came out of the car, got 140 000Km.
Ex owner said compression was bad, this is the only background I've got about that engine.

So, I finally took it into the shop and opened it up all the way. There was only 2 gaskets present : head gasket + exhaust gasket. All other gaskets were missing.


Anyway, let's jump into troubles. Got confused about both the head and one piston.

First, the head, there is cracks between valves on all cylinders. I've read online it's ok. Not much worry about those.
But there is more crack, between one valve and the preheating space; present on three cylinders.
Pictures :
https://ibb.co/FnHx1gs
https://ibb.co/0B5FtGc
https://ibb.co/FX75TYJ

What do you guys thinking?


Second : One piston seems in a pretty bad condition, like if it has been gently smashed.

Regular one :
https://ibb.co/jZYCGZJ
Smashed one :
https://ibb.co/NTrfmNq
More pistons :
https://ibb.co/sFCdZgN

This is piston #4. Don't know what happened in there? No marks on the head, nothing.
Was thinking to file it and put it back?


Thoughts really welcome, thanks all