yup if your block is bored 30 over as most people like to call it, then now u need pistons with a bore size of 4.030 which piston manufactures make and i believe that will turn your 302ci moter into a 306ci motor
igotyofire is absolutely correct. The overbore is usually done if there's extra wear on the cylinder walls, or a piston/ring was damaged. You may or may not notice a power difference, it's a very subtle change.