http://splparts.com/main4/index.htmScroll to the bottom of the the page. My J30 diff was missing a bushing too, plus, supposedly, it's possible for the bushing to tear when you use the J30 diff on the S13 (even if you use longer bolts and washers to brace). This set is solid alum alloy and will never need replacing. The ride isn't any different than stock (since the stock diff housing is solid). I paid $99 for these shipped express. Well worth it IMO. The fit was perfect on one ear, and slightly hard to get in on the other. A rubber mallet and block of wood worked fine, or you could put them in the freezer for an hour or so to shrink the metal a bit.