i can get a free rear, drum to drum, out of a 91 formula 305 tpi a4. the guy says its a 3.23 rear/posi. i believe him about the posi, but i think they are 2.73's. i have a 1986 v6 M5 rear(3.42 7.5" 10 bolt 26 spline) i was thinking that i could use the differential and 28 spline axles from the free rear and put them in my rear and use my 3.42's over again. i read some where that spacers could be used to use a 3 series gear in a 2 series carrier. is the formula rear of that year a 7.5 or 7 5/8" ring gear. i want to make sure that i can use the posi and axles in my rear housing.