There is nothing wrong with that rear. Most housings are not straight. The ends being offset just means it was narrowed correctly with a jig. I narrow rears and this is correct. What I have done for customers for a great deal more cash, is, cut the ends off, jig it, then heat and straighten the tubes by heating and bending. This is very common on rears that have a back brace installed (harder to straighten). The centerline of the carrier does not care where the tubes are located but the centerline of the axle/bearing end is critical.