magnum cracked heads

Sooner or later they burn a seat or leak into the water jacket causing temp rise at idle, and with a/c going.
The psi build and pushes the spring back on the rad cap and fills the overflow up.

Cracks are cracks, they will lead to a failure at some point.

To all these people saying to run them "it's no harm"...
well...I have a set of 302 heads that mag'd cracked that never gave a lick of trouble on the 318 they were on....would any of you buy them and run them...?

Probably not!
Most are plenty repairable by pinning them.
The repairs if done right will last.