Most 216's have cast iron pistons, not aluminum. An engine that's stuck that tight is going to need to be rebuilt once it's freed up, so don't worry about damaging the pistons- - - -they're going to be scrapped anyway when you bore the block. Get a can of KROIL (www.kanolabs.com) and forget about the Propane torch- - - -use acetylene and warm up the pistons with a rosebud tip, then put 2-3 ounces of KROIL into each cylinder and let it sit a few days. Cast iron conducts heat fast enough that a Propane torch will be totally ineffective. As a last resort, use a big hole saw in a variable speed drill motor and cut the tops out of the pistons about 1/2" away from the cylinder walls.
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!