Boring a SBC past .060 requires sonic testing to determine if the cylinder walls are thick enough. Older '50's blocks were a little thicker around the cylinder walls and could go .125 over. That's what the rodder's were doing at that time to get a 327. Eventually, GM cought on and started making 327's (with 4.001" bore standard). From there, you can go another .060......
Watch for heating up, though, if you do it.
