To the best of my recollection, they stopped including build sheets after 1983, although it's possible an '84 may still have one. I don't recall the exact changeover date when they went from alpha-numeric sales codes to alpha (i.e., A38 -> AHB), but it was during or just before the '84 model year. The data on the fender tags will give you the info you need anyway, along with running the VIN through the Mopar VIN decoder.
Rear seat is easy. Two hooks along the bottom. Push down and back to unhook, then pull up from the front. Seat back has 2 7/16 bolts at the bottom, two hooks along the top.