OK, you've got a 256 engine bored .030" oversize. That's basically a 270 block with a 248 crankshaft. You can run .030 over 270 piston rings, which might be easier to find in a parts catalog than a listing for the relatively unknown 256 engine.
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!