if you cant find the stock sizes for whatever reason, you can use different sizes, but still keep the same ratio. for example 14/42 = 0.333 16/48 = 0.333 sprockets are different sizes, but the drive ratio will still be the same. but check www.denniskirk.com they should have everything you need. you can put in your year, make and model and it will search out every part for it.