Yup, 71' 8.5 has bolt in axles. My posi carrier is an original cone style. Has carried my 3650lb Skylark to a best of 12.92 with a best 60' of 1.74 . My planned upgrades will not be enough to get me into rollcage times, 11.49 . The 28 splines will be fine running mid to low 12s, the carrier, not so much. I think if I were to upgrade to a 30 spline, I would go with Strange Axles. Jim