what your up against is what shape is the bore now in? the machinist should be able to tell you. Most small block`s can go over safely to .060 over, but if you plan on going over more it would be wise to have it sonic checked. Last I hear .080 over has become common practice, but I`d recommend sonic checking first.
Don`t have your block bored more than needed, as boring it bigger doesn`t help power output much.