i put an 83 body on a 77. there are a few small things i think were different like how the e brake was ran. also the 77 frame the front frame horns are curved where on the 81 ( i think?) AND later trucks they are cut slanted. different style bumper brackets and possibly bumpers. you need to use the body mounts that are the same year as the frame you plan on using. I.E. taking a 77 body putting it on an 84 frame, use the 84 body mounts.