I believe the main reason the wheels aren't exactly centered is because of the style of the stock adjustable bearings. The passenger side bearing has an adjuster on it to adjust the bearing preload and when it's properly preloaded it pushes the drivers side axle out a little while it's in a little. 3/4" is more than I normally see. My Cuda is off by 1/2" and is what I generally see but if the thrust pin in the center section is worn it makes the offset more. If you do away with the stock type bearings and adjuster setup and use green bearings the axles will be centered.