AM probably has them, CJPonyparts, Late model Restoration, Jegs, Summit all should have them...Depends on the gear ratio how accurate & long they last but they are cheap enough & easy to install. They have gear calculators on their sites or you can find them on the net...There also is a gear speedometer repair kit for the gear in our dash cluster don't remember the applicable years it works in but that is not what you need...Speed Cal is best of course