If your 216 pistons are the domed type, the flattop 235's will lower the compression slightly, but that will be offset by the bigger bore. Just don't try to replace a flat top with a domed piston- - - -there's a possibility of head to piston interference.
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!