Last resort- - - - -drill a series of 1/4" holes around the perimeter of the piston a little inboard of the rings, and break the center out of the piston with a BFH and a punch. Then the remaining piston material can be chipped out with a hammer and a punch. In the very unlikely event the block doesn't have to be bored, a few of us have plenty of cast iron 216 pistons we'll be happy to give you just to get rid of them! Just tell us the bore size- - - -standard or overbored.
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!