Found a 489 what to do with it?

Buy a sure grip unit of your choice, (i prefer the old style clutch type) used, or spring for one of the new units. If the gears and bearings spin nice, (99% of the time they do) put new carrier bearings on there, measure the backlash on the gear (do a search, its simple) then remove the open diff, transfer the ring gear from the open unit to the suregrip, reinstall, set backlash to pevious measurement and your done. Most "shops" will charge you a ton, and you will end up with a noisy gear set.