The simplest and quickest way I have used for preliminary checking for straight is put a set of tires or even just rims on, while it is sitting on floor, rotate the housing around and you will see wheels move in and out as it is rotated. I have seen supposedly STRAIGHT housings that were done with the solid bar narrowing kits when welding still show quite a bit of wheels moving in and out as housing is rotated. Again, quick and simple, but definitely lets you know how straight..... or not!