I would also look for a blazer rear end. Blazers had rear disk brakes and many of them were posi. They all had V6s so you should either get a 3.42 or a 3.73 gear ratio. The 4 wheel drive blazer rear ends were four inches wider than the two wheel drive I believe. If your not looking for disks but still want posi look in the glove box in the S-10. If it has a G-80 code than it is a posi.