1981-1987 on up to 1991 rear seats in crew cabs if you want a direct bolt in. They physically bolt in down to 1973 however the seat belts need to go through the seat bottom to be right and the 3 point system is different on the older ones. Crew cab and Suburban front seats also work but don't tilt forward to access behind the seat and the seat sliders either have to be bent in the rear or use your 1983 ones as the floor contour is different where the rear sliders mount. That is the easiest replacement. All others will require custom mounts.