I just measured a manifold- - - - -the counterbore is about 1/4" deep, and there's a similar depth to the recess in the port in the head- - - - - -plenty of room to handle a reasonable amount of milling and shortening of the rings if necessary.
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!