What is the thickness of the top rings you took off the pistons? It's possible that a previous rebuilder has gotten too energetic with a ring groove cleaner and widened a 1/8" ring groove a little.
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!