I don't know much about chevelle a but are you sure the seat bottom height is the difference? My tempest has a bench seat and there is a difference between the pontiac bench seats and the buick and chevelle ones. I had a buick one in when my original broke, used the bottom and driver side back off the buick and the pass side pontiac back. The hight your shoulders sit is different, the front of the pontiac seat back was lined up with the back of the buick back meaning in the pontiac seats you ride lower in the seat because your leaned back more. The seat tracks were the sane for both, all that said the difference might be in the backs.