I'm planning to put a V6 in my '85 4000qc, but I'm not sure which rear diff to use. It's a 2.8L out of an '92 Audi 80 V6 quattro. Because the mountings on this diff aren't the same , I'm thinking of using one from an ur-q or an ur-q 20 v. I don't know if anybody has performed this swap, but tips are always welcome.