Block decking is usually only a shallow skim cut to assure good head gasket sealing. Head milling is more complicated, as it can result in intake valve burning and altered rocker arm geometry if too much material is removed from the head.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!