$100 for a junkyard one.
i just bought an 88 thunderbird turbo coupe 8.8 rear end 5 lug with disc brakes for $75 to go on my rx7 . I'm going to clean it up and convert to 31 spline. I don't think I'm going to reuse the calipers or rotors. For sure will not be using the 28 spline axles or 28 spline traction-lok. These rear ends are so old now, they take a while to clean, if you have a clean rear on your car already maybe it would be better just to buy a 5 lug and disc conversion kit brand new.