Just picked up a 72 Duster 340 4spd roller a few weeks ago and I haven't found the build sheet just yet, no time. I did pull the rear seat though, no luck. The front buckets were sold off many years back. It could be other places but my question is where are you finding your's? I have had many b-bodies and e-bodies but maybe the a-bodies are finding them in different places, ie: headliner??? Obviously mine was built at the Hamtramick plant.