I do it a bit different then most, and yes, it does cost a bit more... I pick out the wheels and tires I want and get them... This way I'm not stuck with an offset that doesn't look right, also, I prefer having the wheel center close to centered on the width of the rim, better for wheel bearings. You'll also have to decide on the brakes you're going to run, drum or disc and take into account the width required for the drum or rotor. Then, put the wheels and tires under the car with the car at ride height, measure between the inner mounting surfaces on the wheel and either find a rear end matching this dimension, or build one to this width... Costs a bit more, but I just hate having to "make do" with stock stuff that doesn't really fit or look the way I want it to.... Another bonus, when you're all done with the car and decide it's time to "go fast", you can bolt on a good hookin' set of slicks and not worry about breaking a couple of previously used and abused rear axles not designed for the horsepower I'm probably going to put to them, anyway.....