The trick to removing cast iron guides without damaging the head is to drill the guide out until it's only got a wall thickness of 1/16" or a bit more. That relieves most of the press fit and the guide moves a lot easier. Most machine shops stopped using bronze liners sometime ago- - - -too much labor time involved in reaming the guide, fitting the liner, and reaming again for valve stem clearance. Maybe on a race engine - - - -not for general street use!
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!