http://zilvia.net/f/showthread.php?t=506967
after searching i found this. the s13 ring gear is smaller so it causes you to need to move the diff over to one side more which is why it causes it to stick out that little bit and the other to be to far in.
the pic def helped out because ithought it was sticking out way more. but seeing it stick out that little i knew something was wrong. i dont have experience with the j30 diff but thats the info that will help you out