the rarest car i ever owned was a 74 anniversary trans am 455sd 4 speed with T tops.
i have read that only 6 cars were made. the T tops leaked so bad they removed the cars from the assembly line and welded up the roofs where they were.
car was rusted up to the door handles. the floors were sheet metal pop riveted in. i traded to someone who knew what it was. i only paid $200 for it. drove it for 2 weeks. and traded it even up for a 78 little red express with a blown motor with 60k miles. this was the summer of 1980.