Didnt get rid of the stang did you Miles? Anyway a GN rear or a T-type rear is the only direct bolt in that will be the proper width and thats the 8.5 10 bolt. Those can get pretty pricey but if you look around on some G-body forums im sure you could score one for around 600ish. Also a 12 bolt or 10 bolt from an A-body car will bolt in but you will need different rims because the rear is wider. also need a set of control arms that TRZ sells... ICEMAN also sells the A-body swap upper control arms on ebay for about 200 or so...There are also several other kits that will put a 12 bolt or ford 9 inch on the car, one is made by BMR, but they can get expensive. If you dont plan on beating the shit out of the car with a new posi unit the 7.5 should hold up to about 350hp, but if its getting beat on all the time and dead hooking it will be short lived.
Brandon