Cheapo Hemi core .

Yeah, there's various reasons for overheating. The fan modules go bad and the fan motors also. Bottom line is it's VERY common to drop a valve seat after overheating. I have a 5.7 core simply because I got it cheap. I threw the heads away. It destroyed one piston, but the cylinder wall was barely touched, would possibly clean up with just a hone.

If your bosses engine had overheated, just do the usual machine shop checks of the block, but personally, I wouldn't trust those heads. I'm not sure what steps a machine shop can take to make sure the seats don't come out later. Anybody know?