'84 S10 rear is a 26 spline 7.5.. disc brake can be fit but, that's a weakling.. and finding the 2wd 8.5" rear will be impossible.. 9" is a thought, but you can get just about the same strength AND disc brakes w/ a LSD if you get a Ford 8.8 out of an Explorer.. takes just a little coaxing to bolt them in an S10