wheel woogie woes

im pretty sure the 489 number your refering to is just the style of the carrier housing i dont think it would be different in a 742 or 741 housing if its just the axle youre needing just make sure its from an a-body and also if you do find a 8 3/4 in a a-body thats in a wrecking yard make sure its a abody rear end i'd take some measurements from your old one to hopefully get the right one
Terry