The standard overbore is .030". You'll have a tough time finding .010"- or .020"-over pistons. And they're usually more expensive than .030"-over pistons. Don't bore more than .030" over without having the block sonic-checked.

But if the engine's cylinders don't need to be bored, they shouldn't be. Short of needing to "clean-up" the cylinders or unshrouding valves, overboring a block will reap no measurable advantage.

im not sure that the block "needs" to be bored, i plan on boreing, polishing and repainting, wouldnt boring it over increase power or torque, or is there no real benefit of this. i plan on replacing everything pistons, valves, roller rockers, pushrods, springs the whole 9 yards. should i justr have it cleaned and painted with out boreing and just replace all the internals

A .030" overbore nets a measily FOUR cubic inches. Four cubic inches isn't squat.

so should i just have it polished and total rebuild or is there a safe overbore more than .03 that would be significant. what would make it nessesary to overbore. i also intend on going with nos wet nitrous system how would overbore come into play there

Don't know what you mean by "polished". Engine blocked don't get polished. Cranks and heads do.

Boring an engine is for cleaning up the bores OR unshrouding the valves only. It is not (or should not be) done just to gain displacement.