Once you identify what rear end you have you can use this site to find gears.
www.heavytruckparts.net type in your axle info.
If it's not listed a simple phone call to them will probably find exactly what you're looking for. If it's a 3rd member like my 17221 rear is you maybe better off finding the whole 3rd member and swapping it. Pulling one of your axles out and verifying the spline count is something you'll have to do just to be sure. For my axle code there are two different splines 16 and the other 30-something. I have the 16 spline.
