It needs to be a 14bsf out of a 80-87 truck. The 2WD and 4WD are different widths as well, but either should work (2wd will be the same as your current 10b, while a 4WD will be approx. same width as your front). Also, I doubt you will find a 6 lug axle in those years if that is what you're looking for. So far I haven't been able to confirm if 6-lug 14bsf were ever made for the OBS trucks, and believe me I looked. NBS trucks came with them, but if you use one you have to move the spring perches and shock mounts (which is what I did).