Someone on this board mentioned that they did a guts swap with a 3rd gen. Camaro. Maybe try the search feature and see what you come up with.
You can install a posi unit from various other 7.5" GM rear ends. Which ones exactly I am not totally sure of. Certain S10 pick ups, certain 3rd. gen. Camaros and G body Monte Carlo SS's would have posi units.
I agree with Bob that if you don't have experience setting a rear end, you should take it to someone that does.
There is another option, that would be to swap out the whole rear end with one that does have posi. A Monte Carlo SS rear end would swap right in with no mods. If you want a stronger rear end, you can try to hunt down a Buick Gran National or T-Type rear end, these also bolt right in with no mods necessary and come with a 8.5" gear set that is much stronger than the stock unit in your Cutlass now. Both the SS and Buick rears would also come with better gear ratios too.
<a href="http://www.hawaiianflavor.com/Malibu/malibu.html" target="_blank">It's not perfect, but it's mine.</a>
[ April 04, 2003: Message edited by: OddsNEnds ]</p>