cash for clunkers cylinder heads ???

[69heavychevy]

I went to one of the local u pull its and came across about 20-25 pairs of vortec heads on trucks that had been clunkered. I was wondering if the liquid glass they use to destroy the bottom end also damages the heads?? I know your not allowed to pull them from clunkers but i dont usually follow rules anyways. For $30 a head, if they're salvageable sounds like a good deal to me...