When looking at aftermarket axles for your particular Mustang, you will also want to check that your rear differential will be compatible with your upgrade. Moser, Superior and Ford Racing are all excellent brands to choose from. You can either replace your axles with aftermarket versions that have the same amount of splines, or upgrade to an axle with more splines and a larger diameter for added performance. If you choose to use the same number of splines it is easier install them yourself. If you are choosing to upgrade in size you will need to change the rear end differential.